Memory system and memory device

ABSTRACT

According to one embodiment, a memory system includes n memory cells, each capable of storing j bits of data; and a controller. The controller is configured to write a first portion of each of first data to n-th data from among n×j data with consecutive logical addresses to the n memory cells one by one. The first data has a lowest logical address among the n×j pieces of data. The first data to the n-th data have ascending consecutive logical addresses. The controller is configured to write the first portion of one of the first to n-th data as a first bit of the j bits, and write the first portion of another one of the first to n-th data except said one of the first to n-th data as a second bit of the j bits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2019-170378, filed Sep. 19, 2019, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a memory system.

BACKGROUND

A memory system including a memory device and a controller that controlsthe memory device is known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates components and connections in a memory systemaccording to a first embodiment, and related components;

FIG. 2 illustrates functional blocks of a memory controller according tothe first embodiment;

FIG. 3 illustrates components and connections in a memory deviceaccording to the first embodiment;

FIG. 4 illustrates an example of several components and connections in amemory cell array according to the first embodiment;

FIG. 5 illustrates a mapping between a threshold voltage distribution ofmemory cell transistors and data according to the first embodiment;

FIG. 6 illustrates an example of processing data for data writes in thememory controller according to the first embodiment;

FIG. 7 illustrates a flow of data writes in the memory system accordingto the first embodiment;

FIG. 8 illustrates an example of positions where page data are writtenin the memory device according to the first embodiment;

FIG. 9 illustrates a flow of an input and output signal for data writesand ready/busy states in the memory system according to the firstembodiment;

FIG. 10 illustrates an input and output signal, a ready/busy signal, andthe potential of a selected word line over time in a data read in thememory system according to the first embodiment;

FIG. 11 illustrates an example of a flow of data reads in the memorysystem according to the first embodiment;

FIG. 12 illustrates the input and output signal during data reads overtime in the memory system according to the first embodiment;

FIG. 13 illustrates an example for reference of the positions where pagedata are written in a memory device;

FIG. 14 illustrates an example for reference of an input and outputsignal during data reads over time in a memory system;

FIG. 15 illustrates a mapping between a threshold voltage distributionof memory cell transistors and data according to a second embodiment;

FIG. 16 illustrates an example of positions where page data are writtenin the memory devices according to the second embodiment;

FIG. 17 illustrates an input and output signal during data reads overtime in the memory system according to the second embodiment;

FIG. 18 illustrates an input and output signal during data reads overtime in the memory system according to the second embodiment;

FIG. 19 illustrates a second example of positions where page data arewritten in the memory devices according to the second embodiment;

FIG. 20 illustrates components and connections in a memory deviceaccording to a third embodiment;

FIG. 21 illustrates an example of positions where page data are writtenin the memory devices according to the third embodiment;

FIG. 22 illustrates an input and output signal during data reads overtime in the memory system according to the third embodiment;

FIG. 23 illustrates an input and output signal during data reads overtime in the memory system according to the third embodiment;

FIG. 24 illustrates a second example of positions where page data arewritten in the memory devices according to the third embodiment;

FIG. 25 illustrates an example of positions where page data are writtenin the memory devices according to a modification of the thirdembodiment;

FIG. 26 illustrates a mapping between a threshold voltage distributionof memory cell transistors and data according to a fourth embodiment;

FIG. 27 illustrates an example of positions where page data are writtenin the memory devices according to the fourth embodiment;

FIG. 28 illustrates an input and output signal during data reads overtime in the memory system according to the fourth embodiment;

FIG. 29 illustrates an input and output signal during data reads overtime in the memory system according to the fourth embodiment;

FIG. 30 illustrates an input and output signal during data reads overtime in the memory system according to the fourth embodiment;

FIG. 31 illustrates an input and output signal during data reads overtime in the memory system according to the fourth embodiment;

FIG. 32 illustrates a second example of positions where page data arewritten in the memory devices according to the fourth embodiment;

FIG. 33 illustrates an example of positions where page data are writtenin the memory devices according to a fifth embodiment;

FIG. 34 illustrates an example of positions where page data are writtenin the memory devices according to a modification of the fifthembodiment;

FIG. 35 illustrates a mapping between a threshold voltage distributionof memory cell transistors and data according to a sixth embodiment;

FIG. 36 illustrates an example of positions where page data are writtenin the memory devices according to the sixth embodiment;

FIG. 37 illustrates an input and output signal during data reads overtime in the memory system according to the sixth embodiment;

FIG. 38 illustrates an input and output signal during data reads overtime in the memory system according to the sixth embodiment;

FIG. 39 illustrates a second example of mapping between a thresholdvoltage distribution of memory cell transistors and data according tothe sixth embodiment;

FIG. 40 illustrates an example of positions where page data are writtenin the memory devices according to a modification of the sixthembodiment;

FIG. 41 illustrates an example of positions where page data are writtenin the memory devices according to a seventh embodiment;

FIG. 42 illustrates an example of positions where page data are writtenin the memory devices according to a modification of the seventhembodiment;

FIG. 43 illustrates an example of positions where page data are writtenin the memory device according to an eighth embodiment;

FIG. 44 illustrates a mapping between a threshold voltage distributionof memory cell transistors and data according to a ninth embodiment;

FIG. 45 illustrates an example of positions where page data are writtenin the memory devices according to the ninth embodiment;

FIG. 46 illustrates an example of positions where page data are writtenin the memory device according to a 10th embodiment;

FIG. 47 illustrates a mapping between a threshold voltage distributionof memory cell transistors and data according to an 11th embodiment;

FIG. 48 illustrates an example of positions where page data are writtenin the memory devices according to the 11th embodiment;

FIG. 49 illustrates an input and output signal during data reads overtime in the memory system according to the 11th embodiment;

FIG. 50 illustrates components and connections in the memory devicesaccording to a 12th embodiment;

FIG. 51 illustrates components and connections in an address converteraccording to the 12th embodiment;

FIG. 52 illustrates a state of the address converter according to the12th embodiment;

FIG. 53 illustrates a flow of an input and output signal for data writesin the memory system according to the 12th embodiment;

FIG. 54 illustrates an example of positions where page data are writtenas recognized by the memory controller according to the 12th embodiment;

FIG. 55 illustrates an input and output signal during data reads overtime in the memory system according to the 12th embodiment;

FIG. 56 illustrates an example for reference of an input and outputsignal for data writes in a memory system;

FIG. 57 illustrates components and connections in the memory devicesaccording to a 13th embodiment;

FIG. 58 illustrates components and connections in an address converteraccording to the 13th embodiment;

FIG. 59 illustrates a state of the address converter according to the13th embodiment;

FIG. 60 illustrates a flow of an input and output signal for data writesin the memory system according to the 13th embodiment;

FIG. 61 illustrates a flow of an input and output signal for data writesin the memory system according to the 13th embodiment;

FIG. 62 illustrates an example of positions where page data are writtenas recognized by the memory controller according to the 13th embodiment;

FIG. 63 illustrates an input and output signal during data reads overtime in the memory system according to the 13th embodiment;

FIG. 64 illustrates an input and output signal during data reads overtime in the memory system according to the 13th embodiment;

FIG. 65 illustrates an example for reference of an input and outputsignal for data writes in a memory system;

FIG. 66 illustrates functional blocks of a memory controller accordingto a 14th embodiment;

FIG. 67 illustrates a flow of data reads in the memory system accordingto the 14th embodiment;

FIG. 68 illustrates a first example of the state of a command queueduring operations over time in the memory system according to the 14thembodiment;

FIG. 69 illustrates a second example of the state of a command queueduring operations over time in the memory system according to the 14thembodiment;

FIG. 70 illustrates a third example of the state of a command queueduring operations over time in the memory system according to the 14thembodiment;

FIG. 71 illustrates components and connections in a memory systemaccording to a 15th embodiment, and related components;

FIG. 72 illustrates functional blocks of a memory controller accordingto the 15th embodiment;

FIG. 73 illustrates a first example of positions where page data arewritten in the memory devices according to the 15th embodiment;

FIG. 74 illustrates a second example of positions where page data arewritten in the memory devices according to the 15th embodiment; and

FIG. 75 illustrates a third example of positions where page data arewritten in the memory devices according to the 15th embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a memory system includes n(where n is a natural number equal to or greater than 2) memory cells,each capable of storing j (where j is a natural number equal to orgreater than 2) bits of data; and a controller. The controller isconfigured to write a first portion of each of first data to n-th datafrom among n×j data with consecutive logical addresses to the n memorycells one by one. The first data has a lowest logical address among then×j pieces of data. The first data to the n-th data have ascendingconsecutive logical addresses. The controller is configured to write thefirst portion of one of the first to n-th data to as first bit of the jbits, and write the first portion of another one of the first to n-thdata except said one of the first to n-th data as a second bit of the jbits.

Embodiments will now be described with reference to the figures. In thefollowing description, components with substantially the samefunctionalities and configurations will be referred to with the samereference numerals, and repeated descriptions may be omitted. The entiredescription for a particular embodiment also applies to anotherembodiment unless it is explicitly mentioned otherwise or obviouslyeliminated.

Each functional block can be implemented as hardware, computer software,or combination of the both. For this reason, in order to clearlyillustrate that each block can be any of hardware, software orcombination thereof, descriptions will be made in terms of theirfunctionalities in general. It is not necessary that functional blocksare distinguished as in the following examples. For example, some of thefunctions may be implemented by functional blocks different from thoseillustrated below. Furthermore, an illustrated functional block may bedivided into functional sub-blocks.

Moreover, any step in a flow of a method of an embodiment is not limitedto any illustrated order, and can occur in an order different from anillustrated order and/or can occur concurrently with another step.

In the specification and the claims, a phrase of a particular firstcomponent being “coupled” to another second component includes the firstcomponent being coupled to the second component either directly or viaone or more components which are always or selectively conductive.

First Embodiment <1.1. Structure (Configuration)>

FIG. 1 illustrates components and connections in a memory systemaccording to a first embodiment, and related components. As illustratedin FIG. 1, a memory system 100 includes two or more memory devices MCand a memory controller 2. The memory system 100 may be a solid-statedrive (SSD) or an SD™ card, for example. As an example, FIG. 1 and thefollowing description are based on an example in which the memory system100 includes four memory devices MC, namely memory devices MC0, MC1,MC2, and MC3. The memory devices MC may be semiconductor memory chips,for example.

The memory controller 2 is connected to the memory devices MC. Thememory controller 2 receives requests from a host device 200, andoperates on the basis of the request from the host device 200 to controlthe memory devices MC. The memory controller 2 controls the memorydevices MC on the basis of the requests from the host device 200, forexample. Specifically, the memory controller 2 writes data in the memorydevices MC and reads data from the memory devices MC.

The memory controller 2 is connected to the memory devices MC through aNAND bus. The NAND bus transfers a plurality of types of control signalsand an 8-bit input and output signal DQ. Some types of control signalsamong the plurality of types of control signals as well as the input andoutput signal DQ are shared by the memory devices MC0, MC1, MC2, andMC3. On the other hand, other control signals are provided individuallyfor each memory device MC. The control signals include signals ⁻CE, CLE,ALE, ⁻WE, ⁻RE, and ⁻WP, data strobe signals DQS and ⁻DQS, and aready/busy signal RB. The sign “⁻” denotes inverted logic, and indicatesthat a signal denoted by “⁻” is asserted when at a low level. Theready/busy signal RB is prepared individually for each memory device MC,or in other words, the ready/busy signal RB includes ready/busy signalsRB0, RB1, RB2, and RB3 that respectively correspond to the memorydevices MC0, MC1, MC2, and MC3. A chip enable signal ⁻CE is preparedindividually for each memory device MC, or in other words, the chipenable signal ⁻CE includes chip enable signals ⁻CE0, ⁻CE1, ⁻CE2, and⁻CE3 that respectively correspond to the memory devices MC0, MC1, MC2,and MC3.

When asserted, the chip enable signals ⁻CE0, ⁻CE1, ⁻CE2, and ⁻CE3 enablethe memory devices MC0, MC1, MC2, and MC3, respectively. An assertedsignal CLE informs a memory device MC that the input and output signalDQ that is input into that memory device MC in parallel to that signalCLE is a command. An asserted signal ALE informs a memory device MC thatthe input and output signal DQ that is input into that memory device MCin parallel to that signal ALE is an address signal. An asserted signalWE instructs the memory device MC to fetch the input and output signalDQ that are input into the memory device 1 in parallel to the signal⁻WE. An asserted signal RE instructs a memory device MC to output theinput and output signal DQ. The ready/busy signals RB0, RB1, RB2, andRB3 indicate whether the memory device MC that outputs respectivesignals is in a ready state or a busy state. The busy state is indicatedby the low level. The memory device MC accepts commands from the memorycontroller 2 in the ready state, while it does not accept any commandsfrom the memory controller 2 in the busy state.

The input and output signal DQ has a width of 8 bits, and includesinformation such as a command (CMD), write data or read data (DAT), anaddress (Add), and a status (STA). The notation “DQ” suffixed by “<M:0>”(where M is a natural number) indicates that the corresponding signalhas bits from the 0th bit to the Mth bit.

The data strobe signals DQS and DQS designate the timing of capturingthe input and output signal DQ.

<1.1.1. Memory Controller>

FIG. 1 also illustrates a hardware configuration of the memorycontroller 2. As illustrated in FIG. 1, the memory controller 2 includesa host interface 21, a central processing unit (CPU) 22, a random accessmemory (RAM) 23, a read only memory (ROM) 24, a memory interface 25, andan error correction circuit (error correction code, or ECC) 26. Thememory controller 2 executes various operations and some of thefunctions of the host interface 21 and the memory interface 25 by theCPU 22 executing firmware (or, programs) stored in the ROM 24 and loadedin the RAM 23. The firmware is configured such that the memorycontroller 2 can be made to perform the operations described as each ofthe embodiments herein. With this arrangement, a data manager 211, aread controller 212, and a write controller 213 described later areconfigured to operate as described in each of the embodiments.

The host interface 21 is connected to the host device 200 through a bus,and manages communication between the memory controller 2 and the hostdevice 200. The memory interface 25 is connected to the memory devicesMC and manages communication between the memory controller 2 and thememory devices MC.

The error correction circuit (ECC circuit) 26 encodes data that will bewritten to the memory devices MC. Also, the error correction circuit 26decodes data read from the memory devices MC. The encoding and decodingare processes necessary for detecting and correcting errors.Specifically, the error correction circuit 26 performs error-correctingcoding processes on the data that will be written to the memory devicesMC (substantial write data). Depending on the method of generating theerror-correcting code, data that is different from the substantial writedata containing the information for error correction by theerror-correcting coding may be generated. Data containing redundant dataafter the error-correcting coding is written to the memory devices MC asthe write data. Also, in the error-correcting decoding process, theerror correction circuit 26 detects errors in the data read from thememory devices MC, and if errors exist, attempts to correct the errors.

FIG. 2 illustrates functional blocks of the memory controller 2according to the first embodiment. Each functional block is realizableby operations by the CPU 22 following firmware in the RAM 23, a portionof the memory space in the RAM 23, and/or dedicated hardware (or, acircuit).

As illustrated in FIG. 2, the memory controller 2 includes a datamanager 211, a read controller 212, and a write controller 213. The datamanager 211 manages logical addresses of data supplied from the hostdevice 200 and positions (or, physical addresses) of the data in thememory devices MC. For this purpose, the data manager 211 includes anaddress conversion table 221.

The read controller 212 executes a process for reading data from thememory devices MC, on the basis of commands received from the hostdevice 200 for example. Specifically, when requested to read particulardata in the memory system 100 from the host device 200 for example, theread controller 212 references the logical address of the read-requesteddata and the address conversion table 221 to determine the physicaladdress where the read-requested data is stored. The read controller 212transmits a command set giving an instruction to read data from thedetermined physical address to the memory device MC through the memoryinterface 25.

The write controller 213 executes a process for writing data to thememory devices MC, on the basis of a command received from the hostdevice 200 for example. Specifically, when requested to store certaindata in the memory system 100 from the host device 200 for example, thewrite controller 213 determines the position in the memory device MCwhere the data that should be written (or, write data) is to be written,and stores the relationship between the logical address of the writedata and the physical address of the write position in the addressconversion table 221. Subsequently, the write controller 213 transmits acommand set giving an instruction to write the write data to thedetermined physical address to the memory device MC through the memoryinterface 25.

<1.1.2. Memory Device>

FIG. 3 illustrates functional blocks of the memory devices MC accordingto the first embodiment. Each memory device MC includes the functionalblocks illustrated in FIG. 3. Each memory device MC includes componentssuch as a plurality of planes (PB0 and PB1), an input and output circuit11, and a sequencer 12. FIG. 3 illustrates an example in which thememory device MC includes two planes PB0 and PB1, but the firstembodiment is not limited to this example, and three or more planes PBmay also be provided.

The input and output circuit 11 is connected to the memory controller 2through the NAND bus. The sequencer 12 receives commands and addresssignals from the input and output circuit 11, and controls the planes PBon the basis of the commands and address signals.

The planes PB are independent of each other, and can execute data read,write, and erase operations independently of each other. Each plane PBincludes a memory cell array 13, a potential generator 14, a driver 15,a sense amplifier 16, and a row decoder 17. In other words, the planePB0 includes a memory cell array 13_0, a potential generator 14_0, adriver 15_0, a sense amplifier 16_0, and a row decoder 17_0. The planePB1 includes a memory cell array 13_1, a potential generator 14_1, adriver 15_1, a sense amplifier 16_1, and a row decoder 17_1.

Each memory cell array 13 includes a plurality of memory blocks (or,blocks) BLK (i.e., BLK0, BLK1, . . . ). Different planes PB includeblocks BLK with different addresses. Each block BLK is a set of aplurality of string units SU (i.e, SU0, SU1, . . . ). Each string unitSU is a set of a plurality of NAND strings (or, strings) STR (i.e.,STR0, STR1, . . . ), which are not illustrated. Each string STR includesa plurality of memory cell transistors MT.

The potential generator 14 generates various potentials necessary forvarious operations, including data write, read, and erase operations,under control by the sequencer 12. The potential generators 14_0 and14_1 can operate independently of each other and generate potentialsindependently of each other.

The driver 15 receives a plurality of potentials from the potentialgenerator 14 belonging to the same plane PB (or, corresponding potentialgenerator 14), and supplies one or more potentials selected from amongthe received potentials to the corresponding row decoder 17. The rowdecoder 17 receives various potentials from the driver 15, receives anaddress signal from the input and output circuit 11, and transfers thepotentials from the corresponding driver 15 to a block BLK selected onthe basis of the received address signal from among the correspondingmemory cell array 13.

The sense amplifier 16 senses the states of the memory cell transistorsMT in the corresponding memory cell array 13, and on the basis of thesensed states, generates read data and transfers write data to thememory cell transistors MT.

<1.1.3. Memory Cell Array>

FIG. 4 illustrates an example of several components and connections inthe memory cell array 13 according to the first embodiment, illustratingthe components and connections of a single block BLK0, and relatedcomponents. A plurality of the blocks BLK, such as all of the blocks BLKfor example, include all of the components and connections illustratedin FIG. 4.

One block BLK includes a plurality of (for example, four) string unitsSU0 to SU3.

In each block BLK, each of p (where p is a natural number) bit lines BL0to BL(p−1) is connected to one string STR from each of the string unitsSU0 to SU3.

Each string STR includes one select gate transistor ST, a plurality of(eight in the figure as an example) memory cell transistors MT such asMT0 to MT7, and one select gate transistor DT such as DT0, DT1, DT2, orDT3. The transistors ST, MT, and DT are serially coupled in this orderbetween a source line CELSRC and one bit line BL. A memory celltransistor MT includes a control gate electrode (word line WL) and acharge storage layer insulated from the surroundings, and can store datain a nonvolatile manner based on the amount of charge in the chargestorage layer.

Strings STR respectively coupled to different bit lines BL make onestring unit SU. In each string unit SU, the control gate electrodes ofthe memory cell transistors MT0 to MT7 are respectively coupled to wordlines WL0 to WL7. A set of memory cell transistors MT sharing a wordline WL in one string unit SU is referred to as a cell unit (or, memorycell set) CU. Also, the gate electrodes of the respective select gatetransistors DT of the plurality of strings STR in each string unit SUare coupled to each other.

The transistors DT0 to DT3 (in FIG. 4, DT2 and DT3 are not illustrated)belong to the string units SU0 to SU3, respectively. The gate of thetransistor DT0 of each of the plurality of strings STR in the stringunit SU0 is coupled to a select gate line SGDL0. Similarly, the gates ofthe transistors DT1, DT2, and DT3 of each of the plurality of stringsSTR in each of the string units SU1, SU2, and SU3 are coupled to selectgate lines SGDL1, SGDL2, and SGDL3.

<1.1.4. Cell Transistors>

FIG. 5 will be referenced to describe the memory cell transistors MT.Each memory device MC can store two or more bits of data in each of thememory cell transistors MT. FIG. 5 illustrates a mapping between athreshold voltage distribution of memory cell transistors MT that storefour bits of data per memory cell transistor MT and data in the memorysystem according to the first embodiment. The threshold voltage of eachmemory cell transistor MT has a magnitude according to the stored data.In the case of storing four bits per memory cell transistor MT, eachmemory cell transistor MT can be in a state corresponding to a thresholdvoltage from among 16 states. The 16 states are referred to as the “0”,“1”, “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9”, “10”, “11”, “12”, “13”,“14”, and “15” states. Memory cell transistors MT in the “0” state, “1”state, “2” state, “3” state, “4” state, “5” state, “6” state, “7” state,“8” state, “9” state, “10” state, “11” state, “12” state, “13” state,“14” state, and “15” state have threshold voltages ascending in thatorder. The “0” state corresponds to the erase state.

By a data write, a write-target memory cell transistor MT may be kept inthe “0” state or changed to any of the “1” state, “2” state, “3” state,“4” state, “5” state, “6” state, “7” state, “8” state, “9” state, “10”state, “11” state, “12” state, “13” state, “14” state, or “15” state, onthe basis of the data to be written. A memory cell transistor MT in the“0” state is a memory cell transistor MT whose threshold voltage is notraised even after a data write, but in the following, an operation inwhich a memory cell transistor MT is kept in the “0” state by a datawrite is also referred to as a write.

Four bits of data are assignable in any format to each state. In thefirst embodiment, each state is treated as having the following four-bitdata. In the following “ABCD” notation, A, B, C, and D represent thevalues of the top, upper, middle, and lower bits, respectively.

“0” State: “1111” “1” State: “1110” “2” State: “0110” “3” State: “0010”“4” State: “0000” “5” State: “0001” “6” State: “0011” “7” State: “0111”“8” State: “0101” “9” State: “1101” “10” State: “1001” “11” State:“1011” “12” State: “1010” “13” State: “1000” “14” State: “1100” “15”State: “0100”

Even a plurality of memory cell transistors MT that store identicalfour-bit data can have different threshold voltages due to variations inthe characteristics of the memory cell transistors MT.

In order to determine the data stored in a data-read-target memory celltransistor (selected memory cell transistor) MT, the state of theselected memory cell transistor MT is determined. The range within whichthe threshold voltage of the selected memory cell transistor MT falls isused to determine the state of the selected memory cell transistor MT.To determine the range of the threshold voltage of the selected memorycell transistor MT, it is determined whether or not the selected memorycell transistor MT has a threshold voltage exceeding a particular readvoltage VCGR. The memory cell transistor MT having a threshold voltageequal to or higher than the read voltage VCGR remains OFF even whilereceiving the read voltage VCGR at its control gate electrode. Incontrast to this, the memory cell transistor MT having a thresholdvoltage lower than the read voltage VCGR remains ON while receiving theread voltage VCGR at its control gate electrode.

The reads for determining whether the selected memory cell transistor MTis in a state above the “0” state, “1” state, “2” state, “3” state, “4”state, “5” state, “6” state, “7” state, “8” state, “9” state, “10”state, “11” state, “12” state, “13” state, and “14” state are referredto as 1R (read), 2R, 3R, 4R, 5R, 6R, 7R, 8R, 9R, 10R, 11R, 12R, 13R,14R, and 15R, respectively. In 1R, 2R, 3R, 4R, 5R, 6R, 7R, 8R, 9R, 10R,11R, 12R, 13R, 14R, and 15R, read voltages V1, V2, V3, V4, V5, V6, V7,V8, V9, V10, V11, V12, V13, V14, and V15 may be used, respectively. Theread voltages V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13,V14, and V15 have default magnitudes, for example.

The read voltage V1 is higher than the highest threshold voltage of thememory cell transistor MT in the “0” state, and lower than the lowestthreshold voltage of the memory cell transistor MT in the “1” stateimmediately after being written.

Similarly, for each of the cases of α (where α is a natural number) from2 to 15, the read voltage Vα is higher than the highest thresholdvoltage of the memory cell transistor MT in the “(α−1)” stateimmediately after being written, and lower than the lowest thresholdvoltage of the memory cell transistor MT in the “a” state immediatelyafter being written.

The group of data of the bits at the same positions (or, digits) of thememory cell transistors MT in a cell unit CU forms a page. The group ofdata of the most-significant (or, first-digit) bits (or, top bits) ofthe memory cell transistors MT in each cell unit CU is referred to asthe top page. The group of data of the second most-significant bits (or,upper bits) of the memory cell transistors MT in each cell unit CU isreferred to as the upper page. The group of data of the thirdmost-significant bits (or, middle bits) of the memory cell transistorsMT in each cell unit CU is referred to as the middle page. The group ofdata of the least-significant (or, fourth-digit) bits (or, lower bits)of the memory cell transistors MT in each cell unit CU is referred to asthe lower page.

The data of each page is determined by reads using a plurality of readvoltages VCGR with different magnitudes. Which magnitudes of the readvoltage VCGR to use are determined on the basis of which combinations offour-bit data are mapped to each state from the “0” state to the “15”state. In the example of the mapping to the groups of bits (or, bitsets) of the states in FIG. 5, the state of each bit in the lower pageis determined by 1R, 5R, and 12R. In other words, the selected memorycell transistor MT determined to be between the read voltage V1 and theread voltage V5 by 1R and 5R can be determined to be storing 0 in thelower bit. In a similar manner, by using 1R, 5R, and 12R to determinewhether each selected memory cell is in the “0” state, in any of the“1”, “^(2”) , “3”, and “4” states, in any of the “5”, “6”, “7”, “8”,“9”, “10”, and “11” states, or in any of the “12”, “13”, “14”, and “15”states, it is possible to determine whether each selected memory cell isstoring “0” data or holding “1” data in the lower bit. The use of one ormore read voltages to read (or, determine) the data in the lower page ofthe selected cell unit CU is referred to as a lower page read.

Reads of the middle page, the upper page, and the top page are similar,and are performed as follows based on the example of the mapping ofstates and bit sets in FIG. 5.

The value of the middle bit of each selected memory cell transistor MTcan be determined by 4R, 6R, 8R, 11R, and 13R. The use of one or moreread voltages to read the data in the middle page of the selected cellunit CU is referred to as a middle page read.

The value of the upper bit of each selected memory cell transistor MTcan be determined by 3R, 7R, 10R, and 14R. The use of one or more readvoltages to read the data in the upper page of the selected cell unit CUis referred to as an upper page read.

The value of the top bit of each selected memory cell transistor MT canbe determined by 2R, 9R, and 15R. The use of one or more read voltagesto read the data in the top page of the selected cell unit CU isreferred to as a top page read.

In the mapping of states and bit sets in FIG. 5, three, five, four, andthree read voltages VCGR are used for the lower, middle, upper, and toppage reads, respectively. Such a mapping is referred to as a “3543mapping” using the numbers of read voltages VCGR needed for the lower,middle, upper, and top page reads. In other words, the notation “HIJKmapping” (wherein H, I, J, and K are natural numbers) indicates mappingin which H, I, J, and K read voltages VCGR are used for the lower,middle, upper, and top page reads, respectively.

A page whose data can be determined by applying the smallest number ofread voltages VCGR may be referred to as a fast page. Also, a page whosedata can be determined by applying a number of read voltages VCGR otherthan the smallest number may be referred to as a non-fast page. In theexample of the 3543 mapping in FIG. 5, the lower page and the top pagecorrespond to fast pages, while the middle page and the upper pagecorrespond to non-fast pages.

<1.2. Operations> <1.2.1. Data Writes>

The memory controller 2 writes data to the memory devices MC asdescribed below.

FIG. 6 illustrates an example of processing data for data writes in thememory controller 2 according to the first embodiment. As illustrated inthe uppermost row of FIG. 6, the memory controller 2 receives a request(or, command) to store data of a certain size in the memory system 100,together with the target data of the store request, from the host device200. The store-request-target data is referred to as the store-requesteddata.

When received by the memory controller 2, the store-requested data isheld in the RAM 23. The write controller 213 generates a plurality ofpage data from the store-requested data as illustrated in the lowermostrow of FIG. 6. Each piece of page data corresponds to one square on thelowermost row of FIG. 6, has a size equal to or less than the size ofthe page, and the write thereof is managed in data units of the pagesize. Hereinafter, data of the page size may be simply referred to aspage data. When written, the page data corresponds to write data. Eachpiece of page data to be written (or, write page data) has a logicaladdress assigned by the write controller 213. In the example of FIG. 6,each piece of write page data has a unique logical address from PG0 toPG7. Such generation of a plurality of write page data fromstore-requested data can be performed according to any method, anexample of which is described below.

As illustrated on the second row of FIG. 6, by dividing thestore-requested data into a plurality of parts (referred to as dataunits DU) and performing error-correcting coding on each data unit DU,the write controller 213 generates write page data derived from the dataunits DU. In the example of FIG. 6, the store-requested data is dividedinto eight data units DU (DU0 to DU7). The data units DU0 to DU7 can bearranged in that order or arranged at arbitrary positions in thestore-requested data. Each data unit DU has a size enabling the set ofone data unit DU and redundant data generated for that data unit DU tobe equal to or smaller than the page size. The write controller 213controls the error correction circuit 26 to generate redundant data RD0to RD7 for each of the data units DU0 to DU7.

The write controller 213 assigns a logical address to the write pagedata containing the set of each data unit DU and the correspondingredundant data RD. In the example of FIG. 6, the logical address PG0 isassigned to the write page data containing the set of the data unit DU0and the redundant data RD0. Similarly, for each of the cases of β from 1to 7, the logical address PGβ is assigned to the write page datacontaining the data unit DU(and the redundant data RDβ. Hereinafter, thewrite page data assigned the logical address PG0 may be referred to asthe write page data (or simply the page data) PG0. Similarly, the writepage data assigned the logical address PGz (where z is a natural number)may be referred to as the write page data PGz.

Data processing as illustrated in FIG. 6 can be performed in order ofascending values of z in “DUz” for the data units DU0 to DU7, forexample. However, the first embodiment is not limited to this example,and the data units DU0 to DU7 can be processed in any order.

The memory controller 2 (particularly, the write controller 213) writesthe write page data PGz to the memory devices MC according to the methoddescribed below.

The memory controller 2 writes n pieces of page data PG havingconsecutive logical addresses one at a time to n planes PB capable ofoperating independently or to n memory devices MC, and additionally,writes one (first page data) from among the n pieces of page data PG toa certain fast page, and writes the remaining (n−1) pieces of page dataPG to pages (fast pages or non-fast pages) other than the page to whichthe first page data is written. As an example, the write page data PG iswritten page by page to one cell unit CU, but an embodiment is notstrictly limited thereto, and the write page data PG may also be writtento only one memory cell transistor of one selected cell unit in one cellunit CU. A specific example according to the first embodiment of a writewith features like the above is described below.

FIG. 7 illustrates a flow of data writes in the memory system 100according to the first embodiment. Particularly, FIG. 7 illustrates aflow for writing eight pieces of page data PG with consecutive logicaladdresses as illustrated in FIG. 6 to a certain memory device MCw (wherew is 0 or a natural number). Hereinafter, the selected cell unit CU ofthe plane PBk of the memory device MCw is referred to as the “selectedcell unit CUswk”.

The eight pieces of page data PG are written to four pages of a selectedcell unit CUsw0 in the plane PB0 and four pages of a selected cell unitCUsw1 in the plane PB1 of a certain memory device MC. Hereinafter, thememory device MC0 is used as an example. The area where the page data PGis written is referred to as a memory area unit MA. The addresses of thetwo selected cell units CUs forming a memory area unit MA (the addressesof the connected word lines WL) may be same or different between theplanes PB0 and PB1. Hereinafter, in the current example of a certainnumber (in this example, eight) of consecutive logical addresses, thememory area unit MA is the set of the lower, middle, upper and top pagesof the cell unit CUs00 in the plane PB0 and the lower, middle, upper,and top pages of the cell unit CUs01 in the plane PB1. Hereinafter, thecase of writing write page data PG0 to PG7 like in FIG. 6 will bedescribed as an example. The same applies to any other eight pieces ofpage data PGz to PG(z+7) with consecutive logical addresses, and thewrite of the page data PG0 to PG7 described below respectively applies.

The write controller 213-divides the plurality of page data PG into aplurality of groups according to the rules described below, and writesthe page data PG in each group to the memory devices MC according to therules described below. Hereinafter, a group of page data PG is referredto as a data set.

The write controller 213 forms a data set from two pieces of page dataPG with consecutive logical addresses. Specifically, the writecontroller 213 forms a data set from page data PGx (where x is 0 or anatural number) and PG(x+1). Subsequently, the write controller 213writes one of the two pieces of write data in the data set to the planePB0, and writes the other piece to the plane PB1. Furthermore, the writecontroller 213 writes the page data PGx having the lower logical addressout of the page data PGx and PG(x+1) to a fast page among the fourpages, and writes the write page data PG(x+1) having the higher logicaladdress out of the page PGx and PG(x+1) to a non-fast page among thefour pages.

As illustrated in FIG. 7, the memory controller 2 sets a parameter r tothe lowest logical address among the plurality of page data PG that willbe written to a single memory area unit MA (step ST1). In the exampleillustrated in FIG. 7, r is set to 0. The write controller 213 writesthe data set of the page data PGr and PG(r+1). The write of a data setis repeated multiple times, and in the first loop, r is 0. First, thewrite controller 213 writes the page data PGr to a free (or, erased)fast page of the plane PB0 in the memory area unit MA (step ST3). Next,the write controller 213 writes the page data PG(r+1) to a free non-fastpage of the plane PB1 in the memory area unit MA (step ST4).

The write controller 213 writes the data set of the page data PG(r+2)and PG(r+3). Specifically, first, the write controller 213 writes thepage data PG(r+2) to a free fast page of the plane PB1 in the memoryarea unit MA (step ST6). Next, the write controller 213 writes the pagedata PG(r+3) to a free non-fast page of the plane PB0 in the memory areaunit MA (step ST7).

The write controller 213 determines whether or not the write of all ofthe page data PG that will be written to the memory area unit MA hasbeen completed (step ST8). In this example, it is determined whetherr=7. If completed (Yes branch), the flow in FIG. 7 ends. If the write ofall page data PG has not been completed (No branch), the processproceeds to step ST9.

In step ST9, the write controller 213 sets r=r+4. In other words, 4 isadded to the current value of r. Step ST9 continues to step ST3.

FIG. 8 illustrates an example of positions where the page data PG iswritten in the memory device MC according to the first embodiment.Specifically, FIG. 8 illustrates an example of the positions where thepage data PG is written by the write in FIG. 7, and illustrates thememory device MC0 as an example.

As illustrated in FIG. 8, the page data PG0 is written to a fast page,such as the lower page for example, of the plane PB0, while the pagedata PG1 is written to a non-fast page, such as the middle page forexample, of the plane PB1.

The page data PG2 is written to a fast page, such as the lower page forexample, of the plane PB1, while the page data PG3 is written to anon-fast page, such as the middle page for example, of the plane PB0.

The page data PG4 is written to a fast page, such as the top page forexample, of the plane PB0, while the page data PG5 is written to anon-fast page, such as the upper page for example, of the plane PB1.

The page data PG6 is written to a fast page, such as the top page forexample, of the plane PB1, while the page data PG7 is written to anon-fast page, such as the upper page for example, of the plane PB0.

The write in FIG. 8 is an example, and the first embodiment is notlimited to this example. For example, page data having a lower logicaladdress (for example, the page data PG0 and/or PG2) may be written tothe top page, while the page data PG1 and PG3 may be written to theupper page. In this case, page data having a higher logical address (forexample, the page data PG4 and/or PG5) may be written to the lower page,while the page data PG6 and PG7 may be written to the middle page.

FIG. 9 illustrates a flow of the input and output signal DQ for datawrite and ready/busy states in the memory system 100 according to thefirst embodiment. More specifically, FIG. 9 illustrates an example ofthe input and output signal DQ flowing from the memory controller 2 tothe memory device MC0 for performing the data write in FIG. 8.

For example, the memory controller 2 instructs the memory device MC0 towrite the page data PG0 to PG7 in order of ascending logical address.FIG. 9 is based on this example.

As illustrated in FIG. 9, first, the memory controller 2 transmits thesignal DQ for writing the page data PG0. In other words, the memorycontroller 2 transmits the page data PG0 and a command set giving aninstruction to write the page data PG0 to the lower page of the selectedcell unit CUs00 of the plane PB0. For this purpose, the memorycontroller 2 transmits a command 01h, a command 80h, an address Add, thepage data PG0, and a command 1Ah, in that order, for example. Thecommand 01h designates the lower page. In other words, the command 01hdesignates that the target of the instruction indicated by the set ofcommands following the command 01h is the lower page. The command 80hindicates a write, and the command 1Ah indicates that the data that willbe written to the selected cell unit CUs follows. The address Adddesignates the plane PB0 while also designating the block BLK and stringunit SU containing the cell unit CUs00 as well as the word line(selected word line) WL coupled to the cell unit CUs00. The address Addis transmitted over five cycles for example, and is illustrated as onecycle in the diagram. Upon receiving the command 1Ah, the memory deviceMC0 temporarily enters a busy state, and after that enters a readystate.

Thereafter, the memory controller 2 sequentially transmits signals DQfor writing the page data PG1 to PG7 in a similar manner to the signalDQ for writing the page data PG0. The differences between the signals DQfor writing the page data PG1 to PG7 and the signal DQ for writing thepage data PG0 are the designated plane PB, the designated page, and thepage data PG. The differences between the signal DQ for writing the pagedata PG7 and the signal DQ for writing the page data PG0 are thedesignated plane PB and the designated page data, and in addition, acommand 10h is included instead of the command 1Ah. To designate themiddle page, the upper page, and the top page, the memory controller 2transmits the commands 02h, 03h, and 04h, respectively, instead of thecommand 01h.

Specifically, to write the page data PG1, the memory controller 2transmits the page data PG1 and a command set giving an instruction towrite the page data PG1 to the middle page of the plane PB1.

After transmitting the signal DQ for writing the page data PG1, thememory controller 2 transmits the page data PG2 and a command set givingan instruction to write the page data PG2 to the lower page of the planePB1.

After transmitting the signal DQ for writing the page data PG2, thememory controller 2 transmits the page data PG3 and a command set givingan instruction to write the page data PG3 to the middle page of theplane PB0.

After transmitting the signal DQ for writing the page data PG3, thememory controller 2 transmits the page data PG4 and a command set givingan instruction to write the page data PG4 to the top page of the planePB0.

After transmitting the signal DQ for writing the page data PG4, thememory controller 2 transmits the page data PG5 and a command set givingan instruction to write the page data PG5 to the upper page of the planePB1.

After transmitting the signal DQ for writing the page data PG5, thememory controller 2 transmits the page data PG6 and a command set givingan instruction to write the page data PG6 to the top page of the planePB1. The memory device MC0 receives the command 10h in the command setdesignating the write of the page data PG6, and writes the page dataPG0, PG3, PG4, and PG7 to the cell unit CUs00 of the plane PB0.

After transmitting the signal DQ for writing the page data PG6, thememory controller 2 transmits the page data PG7 and a command set givingan instruction to write the page data PG7 to the upper page of the planePB0. When the memory device MC0 receives the command 10h in the commandset designating the write of the page data PG7, the memory device MC0writes the page data PG1, PG2, PG5, and PG6 to the cell unit CUs00 ofthe plane PB1. During the writes, the memory device MC0 stays in thebusy state. When the writes is completed, the memory device MC0 returnsto the ready state.

<1.2.2. Data Read>

FIG. 10 illustrates the input and output signal DQ, the ready/busysignal RB, and the potentials of the selected word lines WL over time indata reads in the memory system 100 according to the first embodiment.FIG. 10 successively illustrates data reads from the lower page, themiddle page, the upper page, and the top page of the selected cell unitCUs in a certain plane PB. However, FIG. 10 is intended to merelyillustrate data reads from the lower page, the middle page, the upperpage, and the top page of the selected cell unit CUs, and theillustrated order of the data-read-target pages has no significance.

As illustrated in FIG. 10, to read from the lower page, the memorycontroller 2 transmits a command set giving an instruction to read datafrom the lower page of the selected cell unit CUs. For this purpose, thememory controller 2 transmits the command 01h, a command 00h, theaddress Add, and a command 30h, in that order, for example. The command00h declares that the transmission of an address follows, and thecommand 30h gives an instruction to read data from the page of thedesignated address. An address Add designates the plane PB, the blockBLK and string unit SU that contain the selected cell unit CUs, and theselected word line WL. Upon receiving the command 30h, the memory deviceMC starts a lower page read.

To read data from the designated page, the memory device MC applies aplurality of read voltages VCGR determined according to the designatedpage to the selected word line WL. Subsequently, the memory deviceperforms a single-level reads using respective read voltages VCGR, andhold the results in the latch in the sense amplifier 16. A single-levelread refers to obtaining a set of one-bit data determined on the basisof whether or not the selected memory cell transistor MT has a thresholdvoltage equal to or higher than the read voltage VCGR. By taking asingle-level read at each read voltage VCGR, a result of thesingle-level read with the read voltage VCGR is obtained, and byperforming logical operations on the single-level read data respectivelybased on the plurality of single-level reads obtained in this way, pagedata is obtained. Details are as follows.

As illustrated in FIG. 10 and also described with reference to FIG. 5,to perform a lower page read, the memory device MC successively appliesthe read voltages V1, V5, and V12. The memory device MC performs asingle-level read (1R, 5R, or 12R) while each of the read voltages V1,V5, and V12 is applied, holds the results in a data latch, and performslogical operations on the results of the single-level reads to obtainthe lower page data. The memory device MC, following an instruction (thesignal RE) from the memory controller 2, transmits the obtained lowerpage data (L-DAT) to the memory controller 2.

The middle page read, the upper page read, and the top page read aresimilar. For the middle page read, the memory device MC successivelyapplies the read voltages V4, V6, V8, V11, and V13. The memory device MCperforms a single-level read (4R, 6R, 8R, 11R, or 13R) whilecorresponding one of the read voltages V4, V6, V8, V11, and V13 isapplied, holds the results in a data latch, and performs logicaloperations on the results of the single-level reads to obtain the middlepage data. The memory device MC, following an instruction from thememory controller 2, transmits the obtained middle page data (M-DAT) tothe memory controller 2.

For the upper page read, the memory device MC successively applies theread voltages V3, V7, V10, and V14. Additionally, the memory device MCperforms a single-level read (3R, 7R, 10R, or 14R) while correspondingone of the read voltages V3, V7, V10, and V14 is applied, holds theresults in a data latch, and performs logical operations on the resultsof the single-level reads to obtain the upper page data. The memorydevice MC, following an instruction from the memory controller 2,transmits the obtained upper page data (U-DAT) to the memory controller2.

For the top page read, the memory device MC successively applies theread voltages V2, V9, and V15. The memory device MC performs asingle-level read (2R, 9R, or 15R) while corresponding one of the readvoltages V2, V9, and V15 is applied, holds the results in a data latch,and performs logical operations on the results of the single-level readsto obtain the top page data. The memory device MC, following aninstruction from the memory controller 2, transmits the obtained toppage data (T-DAT) to the memory controller 2.

FIG. 11 illustrates an example of a flow of data reads in the memorysystem 100 according to the first embodiment. Particularly, FIG. 11illustrates a data read from one memory area unit MA of a certain memorydevice MC. The memory area unit MA is inside the memory device MC0, forexample.

As illustrated in FIG. 11, in step ST11, the memory controller 2transmits a command set giving an instruction to read page data PGt(where t is 0 or an even natural number) to the memory device MC0. Whenthe memory device MC0 receives the command set, the memory device MC0 instep ST12 starts the read of the page data PGt.

In step ST13, the memory controller 2 instructs the memory device MC toread the page data PG(t+1). When the memory device MC0 receives thecommand set, the memory device MC0 in step ST14 starts the read of thepage data PG(t+1).

In step ST16, the read of the page data PGt in the memory device MC0 iscompleted. In step ST17, the memory controller 2 instructs the memorydevice MC0 to output the page data PGt.

In step ST18, the read of the page data PG(t+1) in the memory device MC0is completed. In step ST19, the memory controller 2 instructs the memorydevice MC0 to output the page data PG(t+1).

In step ST21, the memory controller 2 determines whether data reads fromall pages in the read-target memory area unit MA have been completed. Inthe current example, this determination corresponds to determiningwhether t is 7.

In the case where the data reads from all pages in the read-targetmemory area unit MA have not been completed (No branch), the memorycontroller 2 sets t==t+2 in step ST22. Step ST22 continues to step ST11.In the case where the data reads from all pages in the read-targetmemory area unit MA have been completed (Yes branch), the process ends.

FIG. 12 illustrates the flow of the input and output signal DQ duringdata reads over time in the memory system 100 according to the firstembodiment. Particularly, FIG. 12 illustrates the states between theoperations in FIG. 11, and illustrates reads from the memory area unitMA, or in other words, data reads from the four pages of each of theselected cell units CUs00 and CUs01, which are respectively from theplane PB0 and the plane PB1.

The memory controller 2 reads data in units of data sets from a memoryarea unit MA, and reads some page data PG in parallel from each dataset. Data sets can be read in any order, but reads can be performed inorder of ascending logical address of the page data PG for example.Hereinafter, a specific example is described.

As illustrated in FIG. 12, the memory controller 2 instructs the memorydevice MC0 to read the data sets of the page data PG0 and PG1 inparallel. For this purpose, the memory controller 2 transmits a commandset giving an instruction for a lower page read to the selected cellunit CUs00 of the plane PB0, and also transmits a command set giving aninstruction for a middle page read to the selected cell unit CUs01 ofthe plane PB1. The lower page read with respect to the selected cellunit CUs00 of the plane PB0 and the middle page read with respect to theselected cell unit CUs01 of the plane PB1 are performed in parallel. Thetransmitted command sets give an instruction for such a parallel read(multi-plane read) from the planes PB0 and PB1.

As an example, the memory controller 2 transmits a command set giving aninstruction for a multi-plane read of the data in the lower page of theselected cell unit CUs00 of the plane PB0. Such a command includes thecommand 01h specifying the lower page, the command 00h, the address Addspecifying the read-target plane PB0 and selected cell unit CUs00, andthe command 32h, for example. The command 32h indicates that a commandset for a multi-plane read follows. Upon receiving the command set, thememory device MC0 enters the busy state from a time t1. Because thecommand set indicates the data read indicated by the command set as wellas indicating that a command set for a multi-plane read follows, afterentering the busy state for a short time from the time t1, the memorydevice MC0 returns to the ready state at a time t2.

Also, in response to the receipt of the command set by the time t1, thememory device MC0 starts a lower page read (in the diagram, “lowerread”) with respect to the selected cell unit CUs00 of the plane PB0from the time t1. As described above, the lower page read includes 1R,5R, and 12R.

The memory controller 2 transmits a command set for performing a middlepage read as well as a multi-plane read with respect to the selectedcell unit CUs01 of the plane PB1 from the time t2. In other words, thememory device MC0 transmits a command set giving an instruction for amiddle page read with respect to the selected cell unit CUs01 of theplane PB1 from the time t2. The command set indicates that a command setdesignating a data read of the target of the multi-plane read does notfollow, and includes the command 02h indicating the middle page, thecommand 00h, the address Add, and the command 30h, for example. Uponreceiving the command set, the memory device MC0 remains in the busystate.

Also, in response to the receipt of the command set by a time t3, thememory device MC0 starts a middle page read (in the diagram, “middleread”) with respect to the selected cell unit CUs01 of the plane PB1from the time t3. The middle page read with respect to the selected cellunit CUs01 of the plane PB1 and the ongoing lower page read with respectto the selected cell unit CUs00 of the plane PB0 are performed inparallel. As described above, the middle page read includes 4R, 6R, 8R,11R, and 13R.

The lower page read with respect to the selected cell unit CUs00 of theplane PB0 is completed at a time t4, and the lower page data, that is,the page data PG0, can be output from the memory device MC0. The memorydevice MC0 (particularly, the sequencer 12) detects the completion ofthe read and enters the ready state from the time t4. The memorycontroller 2 detects the transition to the ready state, instructs thememory device MC0 to output the page data PG0, and receives the pagedata PG0. At the time t4, the middle page read in the plane PB1 is notyet completed.

While the page data PG0 is being output, the middle page read in theplane PB1 proceeds. The middle page read is completed at a time t5, andthe middle page data, that is, the page data PG1, can be output from thememory device MC0. For example, after the receipt of the page data PG0is completed, the memory controller 2 transmits a status read command tothe memory device MC0 and checks the completion of the middle page read.The status read command is a command instructing the memory device MC totransmit information related to the internal state of the memory deviceMC. Upon receiving the status read command, the memory device MC cantransmit a status indicating whether the process according to thelast-received command (in the current example, the middle page read) iscompleted or not, for example. The memory controller 2 learns of thecompletion of the middle page read through the status read command, andfrom a time t5, instructs the memory device MC0 to output the page dataPG1, and receives the page data PG1.

Thereafter, in a similar manner to the page data PG0 and PG1, the memorydevice MC0 performs multi-plane reads of the remaining data sets in theselected cell units CUs00 and CUs01. An overview of this process isdescribed below.

When the receipt of the page data PG1 is completed, the memorycontroller 2 reads the page data in the next data set in parallel. As anexample, the memory controller 2 performs a multi-plane read to read thedata set of the page data PG2 and PG3 in parallel. For this purpose, thememory controller 2 transmits a command set giving an instruction for amulti-plane read of the data in the lower page of the selected cell unitCUs01 of the plane PB1, for example. Upon receiving the command set, thememory device MC0 starts a lower page read with respect to the selectedcell unit CUs01 of the plane PB1 from a time t6.

The memory controller 2 transmits a command set giving an instruction toperform a multi-plane read of the data in the middle page of theselected cell unit CUs00 of the plane PB0 from a time t7. Upon receivingthe command set, the memory device MC0 starts a middle page read withrespect to the selected cell unit CUs00 of the plane PB0 from a time t8.The middle page read in the plane PB0 proceeds in parallel with theongoing lower page read in the plane PB1.

The lower page read in the plane PB1 is completed at a time t9, and thelower page data, that is, the page data PG2, can be output from thememory device MC0. The memory controller 2 instructs the memory deviceMC0 to output the page data PG2, and receives the page data PG2 from atime t9.

While the page data PG2 is being output, the middle page read in theplane PB0 continues. After that, the middle page read is completed, andthe middle page data, that is, the page data PG3, can be output from thememory device MC0. The memory controller 2 uses a status read to learnof the completion of the middle page read, and from a time t10,instructs the memory device MC0 to output the page data PG3, andreceives the page data PG3.

When the receipt of the page data PG3 is completed, the memorycontroller 2 reads the page data in the next data set in parallel. As anexample, the memory controller 2 performs a multi-plane read to read thedata set of the page data PG4 and PG5 in parallel. For this purpose, thememory controller 2 transmits a command set giving an instruction for amulti-plane read of the data in the top page of the selected cell unitCUs00 of the plane PB0, for example. Upon receiving the command set, thememory device MC0 starts a top page read with respect to the selectedcell unit CUs00 of the plane PB0 from a time t11.

The memory controller 2 transmits a command set giving an instruction toperform a multi-plane read of the data in the upper page of the selectedcell unit CUs01 of the plane PB1 from a time t12. Upon receiving thecommand set, the memory device MC0 starts an upper page read withrespect to the selected cell unit CUs01 of the plane PB1 from a timet13. The upper page read in the plane PB1 proceeds in parallel with theongoing top page read in the plane PB0.

The top page read in the plane PB0 is completed at a time t14, and thetop page data, that is, the page data PG4, can be output from the memorydevice MC0. The memory controller 2 instructs the memory device MC0 tooutput the page data PG4, and receives the page data PG4 from a timet14.

While the page data PG4 is being output, the upper page read in theplane PB0 continues. After that, the upper page read is completed, andthe upper page data, that is, the page data PG5, can be output from thememory device MC0. The memory controller 2 uses a status read to learnof the completion of the upper page read, and from a time t15, instructsthe memory device MC0 to output the page data PG5, and receives the pagedata PG5.

When the receipt of the page data PG5 is completed, the memorycontroller 2 reads the page data in the next data set in parallel. As anexample, the memory controller 2 performs a multi-plane read to read thedata set of the page data PG6 and PG7 in parallel. For this purpose, thememory controller 2 transmits a command set giving an instruction for amulti-plane read of the data in the top page of the selected cell unitCUs01 of the plane PB1, for example. Upon receiving the command set, thememory device MC0 starts a top page read with respect to the selectedcell unit CUs01 of the plane PB1 from a time t16.

The memory controller 2 transmits a command set giving an instruction toperform a multi-plane read of the data in the upper page of the selectedcell unit CUs00 of the plane PB0 from a time t17. Upon receiving thecommand set, the memory device MC0 starts an upper page read withrespect to the selected cell unit CUs00 of the plane PB0 from a timet18. The upper page read in the plane PB0 proceeds in parallel with theongoing top page read in the plane PB1.

The top page read in the plane PB1 is completed at a time t19, and thetop page data, that is, the page data PG6, can be output from the memorydevice MC0. The memory controller 2 instructs the memory device MC0 tooutput the page data PG6, and receives the page data PG6 from a timet19.

While the page data PG6 is being output, the upper page read in theplane PB0 continues. After that, the upper page read is completed, andthe upper page data, that is, the page data PG7, can be output from thememory device MC0. The memory controller 2 uses a status read to learnof the completion of the upper page read, and from a time t20, instructsthe memory device MC0 to output the page data PG7, and receives the pagedata PG7.

<1.3. Advantages (Advantageous Effects)>

According to the memory system 100 of the first embodiment, the memorycontroller 2 is capable of obtaining data in a short time as describedbelow.

The page data PG0 to PG7 are assumed to be written to a certain memorydevice MC (for example, MC0), as illustrated in FIG. 13 and alsodescribed below. FIG. 13 illustrates an example for reference of thepositions where the page data PG is written in the memory device MC0.

As illustrated in FIG. 13, as the simplest form of writes, each data setof the page data PG0 to PG7 is written to the same pages from among thelower pages, middle pages, upper pages, and top pages in differentplanes PB. In other words, the page data PG0 is written to the lowerpage of the plane PB0, while the page data PG1 is written to the lowerpage of the plane PB1. The page data PG2 is written to the middle pageof the plane PB0, while the page data PG3 is written to the middle pageof the plane PB1. The page data PG4 is written to the upper page of theplane PB0, while the page data PG5 is written to the upper page of theplane PB1. The page data PG6 is written to the top page of the planePB0, while the page data PG7 is written to the top page of the planePB1.

As a result of such a write, it is anticipated that reads of the pagedata PG0 to PG7 will be performed as follows. In other words, the pagedata PG0 and PG1 are read in parallel, the page data PG2 and PG3 areread in parallel, the page data PG4 and PG5 are read in parallel, andthe page data PG6 and PG7 are read in parallel. The command sets, flowof data, and transitions of the ready/busy signal RB during the aboveseries of reads are illustrated in FIG. 14. FIG. 14 illustrates anexample for reference of the input and output signal DQ during datareads over time in the memory system 100.

As illustrated in FIG. 14, the memory controller 2 instructs the memorydevice MC0 to read the page data PG0 and PG1. Upon receiving the commandset, the memory device MC0 starts a lower page read with respect to theselected cell unit CUs00 of the plane PB0, and subsequently starts alower page read with respect to the selected cell unit CUs01 of theplane PB1. The two reads are both reads from the lower page, andtherefore are completed at substantially the same timings. Upon reachinga state where the page data PG0 and PG1 can be output, the memorycontroller 2 instructs the memory device MC0 to output one piece of thedata, such as the page data PG0 for example, and receives the page dataPG0. When the receipt of the page data PG0 is completed, the memorycontroller 2 instructs the memory device MC0 to output the page dataPG1. Therefore, the data reads from the two planes PB0 and PB1 requirean amount of time equal to the operating time of the plane PB0 or PB1,the time to output the page data PG0, and the time to output the pagedata PG1.

Because it is necessary to apply three or four different read voltagesVCGR for each page read, reading data from many pieces of page data istime-consuming, such as in the case of reading data from all pages inthe memory area unit MA.

On the other hand, the page data PG1 cannot be output while the pagedata PG0 is being output even if the preparations for outputting thepage data PG1 are completed, and effective utilization of such time is aconsideration.

The memory controller 2 according to the first embodiment determines awrite destination for each group of first page data and second page datahaving consecutive logical addresses, and writes the first page data toa fast page in a first plane PB out of two planes PB capable ofoperating independently in parallel, while writing the second page datato a non-fast page in the other of the two planes, namely a second planePB. The memory controller 2 reads in parallel the first and second pagedata written in this way. With this operation, the read of the firstpage data from the memory cell array 13 is completed first, and whilethe first page data is being output from the memory device MC, the readof the second page data from the memory cell array 13 can proceed.Therefore, the output of the first page data and part of the read of thesecond page data are performed in parallel, and the wait time until theoutput preparations are completed and the data can be output like in thereference example (FIG. 14) is greatly reduced. For this reason, byproceeding with the read of the second page data during the output ofthe first page data, the first and second page data can be read andoutput efficiently.

Such an advantage of the first embodiment is obtained by configuring thememory area unit MA such that the following conditions are satisfied.Namely, it is necessary to make it possible to read from both a non-fastpage and a fast page in parallel. To achieve the above, page data PGwith consecutive ascending logical addresses of a number equal to y (or,the number of pages per cell unit CU)/b (or, the number of fast pagesper cell unit CU) form a data set, and the memory area unit MA is formedover independently operable planes PB of a number equal to the number ofpieces of page data PG in the data set. In the first embodiment, a cellunit CU has a memory area of four pages in size, and a cell unit CU hastwo fast pages. For this reason, in the first embodiment, the memoryarea unit MA needs two independently operable planes PB, and the memoryarea unit MA spreads over the two independently operable planes PB0 andPB1 in a single memory device MC.

Second Embodiment

The second embodiment is similar to the first embodiment, but themapping is different from the first embodiment. Hereinafter, thefeatures that differ from the first embodiment will be described mainly.

The configuration of the memory system 100 and the memory devices MCaccording to the second embodiment is the same as that of the firstembodiment.

<2.1. Mapping>

In the second embodiment, a 4434 mapping is used. FIG. 15 illustrates amapping between a threshold voltage distribution of memory celltransistors MT that store four bits of data per memory cell transistorMT and data in the memory system according to the second embodiment. Asillustrated in FIG. 15, in the second embodiment, each memory device MCis treated as having the following four-bit data for each state.

“0” State: “1111” “1” State: “1110” “2” State: “1010” “3” State: “1000”“4” State: “1001” “5” State: “0001” “6” State: “0000” “7” State: “0010”“8” State: “0110” “9” State: “0100” “10” State: “1100” “11” State:“1101” “12” State: “0101” “13” State: “0111” “14” State: “0011” “15”State: “1011”

In the 4434 mapping, the data of each page is determined using thefollowing read voltages. Lower page read: 1R, 4R, 6R, and 11R Middlepage read: 3R, 7R, 9R, and 13R Upper page read: 2R, 8R, and 14R Top pageread: 5R, 10R, 12R, and 15R

In the 4434 mapping, the upper page corresponds to the fast page, whilethe lower page, the middle page, and the top page correspond to non-fastpages.

<2.2. Data Writies>

In the second embodiment, each cell unit CU stores data of four pages insize, and the four pages include just one fast page. Based on thisconfiguration, in the second embodiment, the memory area unit MA spreadsover four independently operable planes PB. For this reason, y (thenumber of pages per cell unit CU)/b (the number of fast pages per cellunit CU)=4, and therefore four pieces of write page data PG withconsecutive logical addresses form a data set, and the memory area unitMA is formed over four independently operable planes PB.

Specifically, the memory area unit MA according to the second embodimentspreads over the planes PB0 and PB1 of the memory device MC0 and theplanes PB0 and PB1 of the memory device MC1. Hereinafter, the memoryarea unit MA according to the second embodiment is referred to as thememory area unit MA2.

FIG. 16 illustrates an example of the memory area unit MA2 and positionswhere page data are written in the memory devices MC according to thesecond embodiment. As illustrated in FIG. 16, the memory area unit MA2is the set of the lower, middle, upper, and top pages of a cell unitCUs00 in a plane PB0 of a memory device MC0, the lower, middle, upper,and top pages of a cell unit CUs01 in a plane PB1 of the memory deviceMC0, the lower, middle, upper, and top pages of a cell unit CUs10 in aplane PB0 of a memory device MC1, and the lower, middle, upper, and toppages of a cell unit CUs11 in a plane PB1 of the memory device MC1.

Based on such features of the memory area unit MA2, 16 pieces of pagedata PG with consecutive logical addresses are stored in a single memoryarea unit MA2. As a specific example, FIG. 16 illustrates an example ofthe positions where 16 pieces of page data PG0 to PG15 with consecutivelogical addresses are written in the memory area unit MA2.

For each of the cases where γ is 0, 4, 8, and 12, the page data PGγ,PG(γ+1), PG(γ+2), and PG(γ+3) form a data set.

As illustrated in FIG. 16, the page data PGγ, PG(γ+1), PG(γ+2), andPG(γ+3) in each data set are written one by one to the planes PB0 andPB1 of each of the memory devices MC0 and MC1, and in addition, one ofthe page data PGγ, PG(γ+1), PG(γ+2), and PG(γ+3) is written to a fastpage (upper page) while the remaining three are written to non-fastpages. Also, each piece of page data included in a data set and writtento a non-fast page is written to any of the lower, middle, and toppages. Furthermore, the pages to which the page data PG0 to PG15 arewritten are determined such that four data sets are written to thememory area unit MA2. Insofar as writes are performed in this way, thepositions where the page data PG0 to PG15 are written are not limited tothe example in FIG. 16. As an example, the page data PG written to thenon-fast pages can be written to different one of lower, middle, and toppages.

As illustrated in FIG. 16, the page data PG0 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the middle page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0. Thepage data P32 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG3 iswritten to the top page of the selected cell unit CUs11 in the plane PB1of the memory device MC1.

The page data PG4 is written to the upper page of the selected cell unitCUs00 in the plane PB1 of the memory device MC0. The page data PG5 iswritten to the middle page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG6 is written to the lowerpage of the selected cell unit CUs11 in the plane PET of the memorydevice MC1. The page data PG7 is written to the top page of the selectedcell unit CUs10 in the plane PB0 of the memory device MC1.

The page data PG8 is written to the upper page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the middle page of the selected cell unit CUs11 in the planePB1 of the memory device MC1. The page data PG10 is written to the toppage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG11 is written to the lower page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG12 is written to the upper page of the selected cellunit CUs1 l in the plane PB1 of the memory device MC1. The page dataPG13 is written to the middle page of the selected cell unit CUs10 inthe plane PB0 of the memory device MC1 The page data PG14 is written tothe top page of the selected cell unit CUs01 in the plane PB1 of thememory device MC0. The page data PG15 is written to the lower page ofthe selected cell unit CUs00 in the plane PB0 of the memory device MC0.

<2.3. Data Reads>

FIGS. 17 and 18 illustrate the flow of the input and output signal DQduring data reads over time in the memory system 100 according to thesecond embodiment. FIG. 18 illustrates the state following FIG. 17.

As illustrated in FIGS. 17 and 18, a data read from any of the non-fastpages proceeds in parallel with a data read of a fast page (upper page).

To read the data set containing the page data PG0 to PG3, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. The memory device MC0 receives theinstruction and starts an upper page read in the plane PB0 of the memorydevice MC0 for obtaining the page data PG0. Next, the memory controller2 instructs the memory devices MC0 and MC1 to read the page data PG1,PG2, and PG3. The middle page read in the plane PB1 of the memory deviceMC0 for obtaining the page data PG1, the lower page read in the planePB0 of the memory device MC1 for obtaining the page data PG2, and thetop page read in the plane PB1 of the memory device MC1 for obtainingthe page data PG3 proceed in parallel with the top page read in theplane PB0 of the memory device MC0.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the middle page read in the plane PB1 of the memory deviceMC0, the lower page read in the plane PB0 of the memory device MC1, andthe top page read in the plane PB1 of the memory device MC1 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG4 to PG7, reads the data set containing thepage data PG8 to PG11, and reads the data set containing the page dataPG12 to PG15. For reading any of the data sets, a data read from thefast page of each data set is started first, and after that, data readsfrom the non-fast pages are started. Subsequently, in each data set, alower page read, a middle page read, an upper page read, and a top pageread proceed in parallel over the planes PB0 and PB1 of each of thememory devices MC0 and MC1.

<2.4. Another Example of Writes>

An example of data writes includes write as illustrated in FIG. 19. FIG.19 illustrates a second example of positions where page data are writtenin the memory devices MC according to the second embodiment.

As illustrated in FIG. 19, the page data PG0 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the top page of the selectedcell unit CUs01 in the plane PB1 of the memory device MC0. The page dataPG2 is written to the lower page of the selected cell unit CUs10 in theplane PB0 of the memory device MC1. The page data PG3 is written to themiddle page of the selected cell unit CUs11 in the plane PB1 of thememory device MC1.

The page data PG4 is written to the upper page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG5 iswritten to the top page of the selected cell unit CUs10 in the plane PB0of the memory device MC1. The page data PG6 is written to the lower pageof the selected cell unit CUs1 l in the plane PB1 of the memory deviceMC1. The page data PG7 is written to the middle page of the selectedcell unit CUs00 in the plane PB0 of the memory device MC0.

The page data PG8 is written to the upper page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the top page of the selected cell unit CUs11 in the plane PB1of the memory device MC1. The page data PG10 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG11 is written to the middle page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG12 is written to the upper page of the selected cellunit CUs11 in the plane PB1 of the memory device MC1. The page data PG13is written to the top page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG14 is written to the lowerpage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MC0. The page data PG15 is written to the middle page of theselected cell unit CUs10 in the plane PB0 of the memory device MC1.

<2.5. Advantages>

According to the second embodiment, the memory area unit MA2 spreadsover two memory devices MC including independently operable planes PB,first page data out of a data set containing four pieces of page datahaving four consecutive logical addresses is written to a fast page(upper page), while the remaining page data are written to differentpages than the page where the first page data is written from among thelower, middle, upper, and top pages. During reads of a data set writtenin this way, reads of the page data other than the first page data ofthe data set can proceed while the first page data is being output. Forthis reason, in the case of the 4434 mapping, data can be read andoutput with the same efficiency as the first embodiment.

Third Embodiment

The third embodiment resembles the second embodiment. In the thirdembodiment, the 4434 mapping is used like in the second embodiment.Hereinafter, the features that differ from the second embodiment will bedescribed mainly.

The configuration of the memory system 100 according to the thirdembodiment is the same as that of the first embodiment. On the otherhand, the third embodiment differs from the first embodiment in thedetails of the memory devices MC.

<3.1. Configuration of Memory Devices>

In the third embodiment, unlike the first embodiment, the plurality ofplanes PB in each memory device MC cannot operate independently.

FIG. 20 illustrates functional blocks of a memory device MC according tothe third embodiment. The memory devices MC according to the thirdembodiment may be referred to as the memory devices MCa. As illustratedin FIG. 20, unlike the first embodiment (FIG. 3), each memory device MCadoes not include the potential generator 14_0 and the driver 15_0 forthe plane PB0 and also does not include the potential generator 14_1 andthe driver 15_1 for the plane PB1. Instead, each memory device MCashares a potential generator 14 and a driver 15.

Based on such a configuration of the memory device MCa, for amulti-plane read from the planes PB0 and PB1, the same read voltage VCGRis applied to the planes PB0 and PB1. Therefore, in the planes PB0 andPB1, the same pages from among the lower, middle, upper, and top pagesbecome the targets of the parallel data reads.

<3.2. Data Writes>

In the third embodiment, each cell unit CU stores data of four pages insize, and the four pages include just one fast page. Based on thisconfiguration, in the third embodiment, the memory area unit MA needs tospread over four independently operable planes PB. In the thirdembodiment, the planes PB0 and PB1 in each memory device MC cannotoperate independently. For this reason, the memory area unit MA needs tospread over four memory devices MC.

To this end, the memory area unit MA according to the third embodimentspreads over a plane PB of the memory device MC0, a plane PB of thememory device MC1, a plane PB of the memory device MC2, and a plane PBof the memory device MC3. The memory area unit MA according to the thirdembodiment is referred to as the memory area unit MA3.

FIG. 21 illustrates an example of the memory area unit MA3 and positionswhere page data are written in the memory devices MC according to thethird embodiment. As illustrated in FIG. 21, the memory area unit MA3 isthe set of the lower, middle, upper, and top pages of a selected cellunit CUs0 w in a plane PBw of the memory device MC0, the lower, middle,upper, and top pages of a cell unit CUs1 w in a plane PBw of the memorydevice MC1, the lower, middle, upper, and top pages of a cell unit CUs2w in a plane PBw of a memory device MC2, and the lower, middle, upper,and top pages of a cell unit CUs3 w in a plane PBw of the memory deviceMC3.

Based on such features of the memory area unit MA3, 16 pieces of pagedata PG with consecutive logical addresses are stored in a single memoryarea unit MA3. As a specific example, FIG. 21 illustrates the positionswhere 16 pieces of page data PG0 to PG15 with consecutive logicaladdresses are written in the memory area unit MA3.

For each of the cases where γ is 0, 4, 8, and 12, the page data PGγ, thepage data PG(γ+1), the page data PG(γ+2), and the page data PG(γ+3) forma data set.

As illustrated in FIG. 21, the page data PGγ, PG(γ+1), PG(γ+2), andPG(γ+3) in each data set are written one by one to the memory devicesMC0 to MC3, and in addition, one of the page data PGγ, PG(γ+1), PG(γ+2),and PG(γ+3) is written to a fast page while the remaining three arewritten to non-fast pages. Also, the page data included in a data setand written to a non-fast page is written to any of the lower, middle,and top pages. Furthermore, the pages to which the page data PG0 to PG15are written are determined such that tour data sets are written to thememory area unit MA3. Insofar as writes are performed in this way, thepositions where the page data PG0 to PG15 are written are not limited tothe example in FIG. 21. As an example, the page data written to thenon-fast pages can be written to different one of lower, middle, and toppages.

As illustrated in FIG. 21, the page data PG0 is written to the upperpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the middle page of the selected cell unit CUs1 wof the memory device MC1. The page data PG2 is written to the lower pageof the selected cell unit CUs2 w of the memory device MC2. The page dataPG3 is written to the top page of the selected cell unit CUs3 w of thememory device MC3.

The page data PG4 is written to the upper page of the selected cell unitCUs1 w of the memory device MC1. The page data PG5 is written to themiddle page of the selected cell unit CUs0 w of the memory device MC0.The page data PG6 is written to the lower page of the selected cell unitCUs3 w of the memory device MC3. The page data PG7 is written to the toppage of the selected cell unit CUs2 w of the memory device MC2.

The page data PG8 is written to the upper page of the selected cell unitCUs2 w of the memory device MC2. The page data PG9 is written to themiddle page of the selected cell unit CUs3 w of the memory device MC3.The page data PG10 is written to the top page of the selected cell unitCUs0 w of the memory device MC0. The page data PG11 is written to thelower page of the selected cell unit CUs1 w of the memory device MC1.

The page data PG12 is written to the upper page of the selected cellunit CUs3 w of the memory device MC3. The page data PG13 is written tothe middle page of the selected cell unit CUs2 w of the memory deviceMC2. The page data PG14 is written to the top page of the selected cellunit CUs1 w of the memory device MC1. The page data PG15 is written tothe lower page of the selected cell unit CUs0 w of the memory deviceMC0.

<3.3. Data Reads>

FIGS. 22 and 23 illustrate the flow of the input and output signal DQduring data reads over time in the memory system 100 according to thethird embodiment. FIG. 23 illustrates the state following FIG. 22.

As illustrated in FIGS. 22 and 23, a data read from any of the non-fastpages proceeds in parallel with a data read of a fast page (upper page).

To read the data set containing the page data PG0 to PG3, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. The memory device MC0 receives theinstruction and starts an upper page read of the memory device MC0 forobtaining the page data PG0. Next, the memory controller 2 instructs thememory device MC1 to perform a middle page read for the page data PG1,instructs the memory device MC2 to perform a lower page read for thepage data PG2, and instructs the memory device MC3 to perform a top pageread for the page data PG3. The upper page read in the memory deviceMC0, the middle page read in the memory device MC1, the lower page readin the memory device MC2, and the top page read in the memory device MC3proceed in parallel.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the middle page read in the memory device MC1, the lower pageread in the memory device MC2, and the top page read in the memorydevice MC3 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG4 to PG7, reads the data set containing thepage data PG8 to PG11, and reads the data set containing the page dataPG12 to PG15. For reading any of the data sets, a data read from thefast page of each data set is started first, and after that, data readsfrom the non-fast pages are started. Thus, in each data set, a lowerpage read, a middle page read, an upper page read, and a top page readproceed in parallel over the memory devices MC0, MC1, MC2, and MC3.

<3.4. Another Example of Data Writes>

An example of data writes includes writes as illustrated in FIG. 24.FIG. 24 illustrates a second example of positions where page data arewritten in the memory devices MC according to the third embodiment.

As illustrated in FIG. 24, the page data PG0 is written to the upperpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the top page of the selected cell unit CUs1 w ofthe memory device MC1. The page data PG2 is written to the lower page ofthe selected cell unit CUs2 w of the memory device MC2. The page dataPG3 is written to the middle page of the selected cell unit CUs3 w ofthe memory device MC3.

The page data PG4 is written to the upper page of the selected cell unitCUs1 w of the memory device MC1. The page data PG5 is written to the toppage of the selected cell unit CUs2 w of the memory device MC2. The pagedata PG6 is written to the lower page of the selected cell unit CUs3 wof the memory device MC3. The page data PG7 is written to the middlepage of the selected cell unit CUs0 w of the memory device MC0.

The page data PG8 is written to the upper page of the selected cell unitCUs2 w of the memory device MC2. The page data PG9 is written to the toppage of the selected cell unit CUs3 w of the memory device MC3. The pagedata PG10 is written to the lower page of the selected cell unit CUs0 wof the memory device MC0. The page data PG11 is written to the middlepage of the selected cell unit CUs1 w of the memory device MC1.

The page data PG12 is written to the upper page of the selected cellunit CUs3 w of the memory device MC3. The page data PG13 is written tothe top page of the selected cell unit CUs0 w of the memory device MC0.The page data PG14 is written to the lower page of the selected cellunit CUs1 w of the memory device MC1. The page data PG15 is written tothe middle page of the selected cell unit CUs2 w of the memory deviceMC2.

<3.5. Advantages>

According to the third embodiment, the memory area unit MA3 spreads overfour memory devices MC, first page data out of a data set containingfour pieces of page data having four consecutive logical addresses iswritten to a fast page (upper page), while the remaining page data arewritten to different pages than the page where the first page data iswritten from among the lower, middle, upper, and top pages. During readsof a data set written in this way, reads of the page data other than thefirst page data of the data set can proceed while the first page data isbeing output. For this reason, data can be read and output with the sameefficiency as the first embodiment, even in the case where the memorydevices MC do not include a plurality of independently operable planesPB.

<3.6. Modification>

The third embodiment may also be applied to multi-plane operations.However, in each memory device MC according to the third embodiment, theplanes PB0 and PB1, although capable of operating in parallel, are notcapable of operating independently, and therefore data reads areperformed in parallel from the same pages of cell units CU with the sameaddress in the blocks BLK of the same address in each of the planes PB0and PB1. Based on the above, two pieces of page data PG with consecutivelogical addresses are written to the same pages in the planes PB0 andPB1 of the same memory device MC.

A memory area unit MA3 a according to a modification of the thirdembodiment spreads over the planes PB0 and PB1 of the memory device MC0,the planes PB0 and PB1 of the memory device MC1, the planes PB0 and PB1of the memory device MC2, and the planes PB0 and PB1 of the memorydevice MC3.

FIG. 25 illustrates an example of the memory area unit MA3 a andpositions where page data are written in the memory devices MC accordingto the modification of the third embodiment. For each of the cases whereγ is 0, 4, 8, and 12, the page data PGγ, the page data PG(γ+1), the pagedata PG(γ+2), the page data PG(γ+3), the page data PG(γ+4), the pagedata PG(γ+5), the page data PG(γ+6), and the page data PG(γ+7) form adata set.

As illustrated in FIG. 25, the memory area unit MA3 a is the set of thelower, middle, upper, and top pages of a cell unit CUs00 in a plane PB0of a memory device MC0, the lower, middle, upper, and top pages of acell unit CUs01 in a plane PB1 of the memory device MC0, the lower,middle, upper, and top pages of a cell unit CUs10 in a plane PB0 of amemory device MC1, the lower, middle, upper, and top pages of a cellunit CUs11 in a plane PB1 of the memory device MC1, the lower, middle,upper, and top pages of a cell unit CUs20 in a plane PB0 of a memorydevice MC2, the lower, middle, upper, and top pages of a cell unit CUs21in a plane PB1 of a memory device MC2, the lower, middle, upper, and toppages of a cell unit CUs30 in a plane PB0 of a memory device MC3, andthe lower, middle, upper, and top pages of a cell unit CUs31 in a planePB1 of a memory device MC3.

Based on such features of the memory area unit MA3 a, 32 pieces of pagedata PG with consecutive logical addresses are stored in a single memoryarea unit MA3 a. As a specific example, FIG. 25 illustrates thepositions where 32 pieces of write page data PG0 to PG31 withconsecutive logical addresses are written in the memory area unit MA3 a.

For each of the cases where γ is 0, 8, 16, and 24, the page data PGγ,PG(γ+1), PG(γ+2), PG(γ+3), PG(γ+4), PG(γ+5), PG(γ+6), and PG(γ+7) form adata set. In addition, the page data PGγ and PG(γ+1) form a pair, thepage data PG(γ+2) and PG(γ+3) form a pair, the page data PG(γ+4) andPG(γ+5) form a pair, and the page data PG(γ+6) and PG(γ+7) form a pair.The two pieces of page data PG that form a pair are written to the samepage in different planes PB of the same memory device MC.

As illustrated in FIG. 25, the pairs of page data PG in each data setare written one by one to the memory devices MC0 to MC3, and one of thepairs of page data PG in each data is written to fast pages while theremaining three pairs are written to non-fast pages.

Also, the pairs of page data PG included in a data set and written tonon-fast pages are written to any of the lower, middle, and top pages.Furthermore, the pages to which the page data PG0 to PG31 is written aredetermined such that four data sets are written to the memory area unitMA3 a. Insofar as writes are performed in this way, the positions wherethe page data PG0 to PG31 are written is not limited to the example inFIG. 25. As an example, the page data PG written to the non-fast pagescan be written to different one of lower, middle, and top pages.

As illustrated in FIG. 25, the page data PG0 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the upper page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG2 is written to the middle page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG3is written to the middle page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

The page data PG4 is written to the lower page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG5 iswritten to the lower page of the selected cell unit CUs21 in the planePB1 of the memory device MC2.

The page data PG6 is written to the top page of the selected cell unitCUs30 in the plane PB0 of the memory device MC3. The page data PG7 iswritten to the top page of the selected cell unit CUs31 in the plane PB1of the memory device MC3.

The page data PG8 is written to the upper page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the upper page of the selected cell unit CUs1 l in the planePB1 of the memory device MC1.

The page data PG10 is written to the middle page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG11is written to the middle page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

The page data PG12 is written to the lower page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG13is written to the lower page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG14 is written to the top page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG15 iswritten to the top page of the selected cell unit CUs21 in the plane PB1of the memory device MC2.

The page data PG16 is written to the upper page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG17is written to the upper page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG18 is written to the middle page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG19is written to the middle page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG20 is written to the top page of the selected cell unitCUs00 in the plane PB0 of the memory device MC0. The page data PG21 iswritten to the top page of the selected cell unit CUs01 in the plane PB1of the memory device MC0.

The page data PG22 is written to the lower page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG23is written to the lower page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

The page data PG24 is written to the upper page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG25is written to the upper page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG26 is written to the middle page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG27is written to the middle page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG28 is written to the top page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG29 iswritten to the top page of the selected cell unit CUs11 in the plane PB1of the memory device MC1.

The page data PG30 is written to the lower page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG31is written to the lower page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

For data reads, the basic principle is the same as the data readsaccording to the third embodiment described with reference to FIGS. 22and 23, the difference being that pairs of page data PG are read inparallel. In other words, when each read command set illustrated inFIGS. 22 and 23 is received by each memory device MC, the memory deviceMC reads data in parallel from the same pages of cell units CU with thesame address instructed by the read command set in each of the planesPB0 and PB1. The data obtained by such reads is a pair of page data PG.The memory controller 2 instructs each memory device MC to output a pairof page data PG, and receives the pair of page data PG.

Fourth Embodiment

The fourth embodiment is similar to the second embodiment, and isdifferent from the second embodiment in the mapping. Hereinafter, thefeatures that differ from the second embodiment will be describedmainly.

The configuration of the memory system 100 and the memory devices MCaccording to the fourth embodiment is the same as that of the firstembodiment.

<4.1. Mapping>

In the fourth embodiment, a 1248 mapping is used. FIG. 26 illustrates amapping between a threshold voltage distribution of memory celltransistors MT that store four bits of data per memory cell transistorMT and data in the memory system according to the fourth embodiment. Asillustrated in FIG. 26, in the fourth embodiment, each memory device MCtreats each state as having the following four-bit data.

“0” State: “1111” “1” State: “0111” “2” State: “0011” “3” State: “1011”“14” State: “1001” “5” State: “0001” “6” State: “0101” “7” State: “1101”“8” State: “1100” “9” State: “0100” “10” State: “0000” “11” State:“1000” “12” State: “1010” “13” State: “0010” “14” State: “0110” “15”State: “1110”

In the 1248 mapping, the data of each page is determined using thefollowing read voltages.

Lower page read: 8RMiddle page read: 4R and 12RUpper page read: 2R, 6R, 10R, and 14RTop page read: 1R, 3R, 5R, 7R, 9R, 11R, 13R, and 15R

In the 1248 mapping, the lower page corresponds to the fast page, whilethe middle page, the upper page, and the top page correspond to non-fastpages.

<4.2. Data Writes>

In the fourth embodiment, each cell unit CU stores data of four pages insize, and the four pages include just one fast page. Based on thisconfiguration, in the fourth embodiment, the memory area unit MA2 of thesecond embodiment is used.

FIG. 27 illustrates an example of positions where page data are writtenin the memory devices MC according to the fourth embodiment. As aspecific example, FIG. 27 illustrates the positions where 16 pieces ofwrite page data PG0 to PG15 with consecutive logical addresses arewritten in the memory area unit MA2.

For each of the cases where γ is 0, 4, 8, and 12, the page data PGγ,PG(γ+1), PG(γ+2), and PG(γ+3) form a data set.

As illustrated in FIG. 27, the page data PGγ, PG(γ+1), PG(γ+2), andPG(γ+3) in each data set are written one by one to the planes PB0 andPB1 of each of the memory devices MC0 and MC1, and in addition, one ofthe page data PGγ, PG(γ+1), PG(γ+2), and PG(γ+3) is written to a fastpage (lower page) while the remaining three are written to non-fastpages. Also, each piece of page data PG included in a data set andwritten to a non-fast page is written to any of the middle, upper, andtop pages. Furthermore, the pages to which the page data PG0 to PG15 arewritten are determined such that four data sets are written to thememory area unit MA2. Insofar as writes are performed in this way, thepositions where the page data PG0 to PG15 are written are not limited tothe example in FIG. 27. As an example, the page data PG written to thenon-fast pages can be written to different one of middle, upper, and toppages.

As illustrated in FIG. 27, the page data PG0 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the middle page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0. Thepage data PG2 is written to the upper page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG3 iswritten to the top page of the selected cell unit CUs1 l in the planePB1 of the memory device MC1.

The page data PG4 is written to the lower page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG5 iswritten to the middle page of the selected cell unit CUs10 in the planePB0 of the memory device MC1. The page data PG6 is written to the upperpage of the selected cell unit CUs11 in the plane PB1 of the memorydevice MC1. The page data PG7 is written to the top page of the selectedcell unit CUs00 in the plane PB0 of the memory device MC0.

The page data PG8 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the middle page of the selected cell unit CUs11 in the planePB1 of the memory device MC1. The page data PG10 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG11 is written to the top page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG12 is written to the lower page of the selected cellunit CUs11 in the plane PB1 of the memory device MC1. The page data PG13is written to the middle page of the selected cell unit CUs00 in theplane PB0 of the memory device MC0. The page data PG14 is written to theupper page of the selected cell unit CUs01 in the plane PB1 of thememory device MC0. The page data PG15 is written to the top page of theselected cell unit CUs10 in the plane PB0 of the memory device MC1.

<4.3. Data Reads>

FIGS. 28 to 31 illustrate the flow of the input and output signal DQduring data reads over time in the memory system 100 according to thefourth embodiment. FIGS. 28 to 31 illustrate temporally successivestates in order.

As illustrated in FIGS. 28 and 31, a data read from any of the non-fastpages proceeds in parallel with a data read of a fast page (lower page).

To read the data set containing the page data PG0 to PG3, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. The memory device MC0 receives theinstruction and starts a lower page read in the plane PB0 of the memorydevice MC0 for obtaining the page data PG0. Next, the memory controller2 instructs the memory device MC0 to perform a middle page read for thepage data PG1, instructs the memory device MC1 to perform an upper pageread for the page data PG2, and instructs the memory device MC1 toperform a top page read for the page data PG3. The lower page read inthe plane PB0 of the memory device MC0, the middle page read in theplane PB1 of the memory device MC0, the upper page read in the plane PB0of the memory device MC1, and the top page read in the plane PB1 of thememory device MC1 proceed in parallel.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the middle page read in the memory device MC0, the upper pageread in the memory device MC1, and the top page read in the memorydevice MC1 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG4 to PG7, reads the data set containing thepage data PG8 to PG11, and reads the data set containing the page dataPG12 to PG15. For reading any of the data sets, a data read from thefast page of each data set is started first, and after that, data readsfrom the non-fast pages are started. Thus, in each data set, a lowerpage read, a middle page read, an upper page read, and a top page readproceed in parallel over the planes PB0 and PB1 of each of the memorydevices MC0 and MC1.

<4.4. Another Example of Writes>

An example of data writes includes writes as illustrated in FIG. 32.FIG. 32 illustrates a second example of positions where page data arewritten in the memory devices MC according to the fourth embodiment.

As illustrated in FIG. 32, the page data PG0 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the middle page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0. Thepage data PG2 is written to the upper page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG3 iswritten to the top page of the selected cell unit CUs11 in the plane PB1of the memory device MC1.

The page data PG4 is written to the lower page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG5 iswritten to the middle page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG6 is written to the upperpage of the selected cell unit CUs11 in the plane PB1 of the memorydevice MC1. The page data PG7 is written to the top page of the selectedcell unit CUs10 in the plane PB0 of the memory device MC1.

The page data PG8 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the middle page of the selected cell unit CUs11 in the planePB1 of the memory device MC1. The page data PG10 is written to the upperpage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MC0. The page data PG11 is written to the top page of theselected cell unit CUs00 in the plane PB0 of the memory device MC0.

The page data PG12 is written to the lower page of the selected cellunit CUs11 in the plane PB1 of the memory device MC1. The page data PG13is written to the middle page of the selected cell unit CUs10 in theplane PB0 of the memory device MC1. The page data PG14 is written to theupper page of the selected cell unit CUs00 in the plane PB0 of thememory device MC0. The page data PG15 is written to the top page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

<4.5. Advantages>

According to the fourth embodiment, the 1248 mapping is used instead ofthe 4434 mapping in the second embodiment, but other than the featuresbased on this point, the fourth embodiment has the same features as thesecond embodiment. The same advantages as the second embodiment are alsoobtained with the 1248 mapping.

Fifth Embodiment

The fifth embodiment is similar to the third embodiment, and isdifferent from the third embodiment in the mapping.

The configuration of the memory system 100 and the memory devices MCaccording to the fifth embodiment is the same as that of the firstembodiment.

In the fifth embodiment, the 1248 mapping is used like in the fourthembodiment.

<5.1. Data Writes>

In the fifth embodiment, like the third embodiment, each cell unit CUstores data of four pages in size, and the four pages include just onefast page. Based on this configuration, in the fifth embodiment, thememory area unit MA3 spreads over four memory devices MC as in the thirdembodiment.

FIG. 33 illustrates an example of the memory area unit MA3 and positionswhere page data are written in the memory devices MC according to thefifth embodiment.

For each of the cases where γ is 0, 4, 8, and 12, the page data PGγ, thepage data PG(γ+1), the page data PG(γ+2), and the page data PG(γ+3) forma data set.

As illustrated in FIG. 33, the page data PGγ, PG(γ+1), PG(γ+2), andPG(γ+3) in each data set are written one by one to the memory devicesMC0 to MC3, and one of the page data PGγ, PG(γ+1), PG(γ+2), and PG(γ+3)is written to a fast page (lower page) while the remaining three arewritten to non-fast pages. In addition, each piece of page data PGincluded in a data set and written to a non-fast page is written to anyof the middle, upper, and top pages. Furthermore, the pages to which thepage data PG0 to PG15 are written are determined such that four datasets are written to the memory area unit MA3. Insofar as writes areperformed in this way, the positions where the page data PG0 to PG15 arewritten are not limited to the example in FIG. 33. As an example, thepage data written to the non-fast pages can be written to different oneof middle, upper, and top pages.

As illustrated in FIG. 33, the page data PG0 is written to the lowerpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the middle page of the selected cell unit CUs1 wof the memory device MC1. The page data PG2 is written to the upper pageof the selected cell unit CUs2 w of the memory device MC2. The page dataPG3 is written to the top page of the selected cell unit CUs3 w of thememory device MC3.

The page data PG4 is written to the lower page of the selected cell unitCUs1 w of the memory device MC1. The page data PG5 is written to themiddle page of the selected cell unit CUs2 w of the memory device MC2.The page data PG6 is written to the upper page of the selected cell unitCUs3 w of the memory device MC3. The page data PG7 is written to the toppage of the selected cell unit CUs0 w of the memory device MC0.

The page data PG8 is written to the lower page of the selected cell unitCUs2 w of the memory device MC2. The page data PG9 is written to themiddle page of the selected cell unit CUs3 w of the memory device MC3.The page data PG10 is written to the upper page of the selected cellunit CUs0 w of the memory device MC0. The page data PG11 is written tothe top page of the selected cell unit CUs1 w of the memory device MC1.

The page data PG12 is written to the lower page of the selected cellunit CUs3 w of the memory device MC3. The page data PG13 is written tothe middle page of the selected cell unit CUs0 w of the memory deviceMC0. The page data PG14 is written to the upper page of the selectedcell unit CUs1 w of the memory device MC1. The page data PG15 is writtento the top page of the selected cell unit CUs2 w of the memory deviceMC2.

<5.2. Data Reads>

Data reads follow the basic principle described for the otherembodiments, and particularly resembles the third embodiment. In otherwords, data are read in parallel for each data set, and a data read fromany of the non-fast pages proceeds in parallel with a data read of afast page (lower page).

To read the data set containing the page data PG0 to PG3, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. Next, the memory controller 2 instructs thememory device MC1 to perform a middle page read for the page data PG1,instructs the memory device MC2 to perform an upper page read for thepage data PG2, and instructs the memory device MC3 to perform a top pageread for the page data PG3.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the middle page read in the memory device MC1, the upper pageread in the memory device MC2, and the top page read in the memorydevice MC3 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG4 to PG7, reads the data set containing thepage data PG8 to PG11, and reads the data set containing the page dataPG12 to PG15. For reading any of the data sets, a data read from thefast page of each data set is started first, and after that, data readsfrom the non-fast pages are started.

<5.3. Advantages>

According to the fifth embodiment, the 1248 mapping is used instead ofthe 4434 mapping in the third embodiment, but other than the featuresbased on this point, the fifth embodiment has the same features as thethird embodiment. The same advantages as the third embodiment are alsoobtained with the 1248 mapping.

<5.4. Modification>

Like the modification of the third embodiment, the fifth embodiment mayalso be applied to multi-plane operations in which independent operationis unavailable.

In this modification, like the modification of the third embodiment, thememory area unit MA3 a is used. Hereinafter, the features that differfrom the modification of the third embodiment will be described mainly.

FIG. 34 illustrates an example of positions where page data are writtenin the memory devices MC according to the modification of the fifthembodiment. For each of the cases where γ is 0, 4, 8, and 12, the pagedata PGγ, the page data PG(γ+1), the page data PG(γ+2), the page dataPG(γ+3), the page data PG(γ+4), the page data PG(γ+5), the page dataPG(γ+6), and the page data PG(γ+7) form a data set.

As illustrated in FIG. 34, the page data PG0 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the lower page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG2 is written to the middle page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG3is written to the middle page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

The page data PG4 is written to the upper page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG5 iswritten to the upper page of the selected cell unit CUs21 in the planePB1 of the memory device MC2.

The page data PG6 is written to the top page of the selected cell unitCUs30 in the plane PB0 of the memory device MC3. The page data PG7 iswritten to the top page of the selected cell unit CUs31 in the plane PB1of the memory device MC3.

The page data PG8 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG9 iswritten to the lower page of the selected cell unit CUs1 l in the planePB1 of the memory device MC1.

The page data PG10 is written to the middle page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG11is written to the middle page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG12 is written to the upper page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG13is written to the upper page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG14 is written to the top page of the selected cell unitCUs00 in the plane PB0 of the memory device MC0. The page data PG15 iswritten to the top page of the selected cell unit CUs01 in the plane PB1of the memory device MC0.

The page data PG16 is written to the lower page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG17is written to the lower page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG18 is written to the middle page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG19is written to the middle page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG20 is written to the upper page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG21is written to the upper page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

The page data PG22 is written to the top page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG23 iswritten to the top page of the selected cell unit CUs1 l in the planePB1 of the memory device MC1.

The page data PG24 is written to the lower page of the selected cellunit CUs30 in the plane PB0 of the memory device MC3. The page data PG25is written to the lower page of the selected cell unit CUs31 in theplane PB1 of the memory device MC3.

The page data PG26 is written to the middle page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG27is written to the middle page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

The page data PG28 is written to the upper page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG29is written to the upper page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

The page data PG30 is written to the top page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG31 iswritten to the top page of the selected cell unit CUs21 in the plane PB1of the memory device MC2.

For data reads, the basic principle is the same as data reads accordingto the fifth embodiment, the difference being that pairs of page data PGare read in parallel, like the modification of the third embodiment.

Sixth Embodiment

The sixth embodiment resembles the third embodiment. In the sixthembodiment, each memory device MC stores three bits of data per memorycell transistor MT.

The configuration of the memory system 100 and the memory devices MCaccording to the sixth embodiment is the same as that of the thirdembodiment.

<6.1. Mapping>

In the sixth embodiment, a 133 mapping is used. The notation “HIJmapping” indicates that H, I, and J read voltages VCGR are used for thelower, middle, and upper page reads, respectively.

FIG. 35 illustrates a mapping between a threshold voltage distributionof memory cell transistors MT that store three bits of data per memorycell transistor MT and data according to the sixth embodiment. Asillustrated in FIG. 35, in the sixth embodiment, each memory device MCtreats each state as having the following three-bit data. In thefollowing “ABC” notation, A, B, and C represent the values of the upper,middle, and lower bits, respectively.

“0” State: “111” “1” State: “101” “2” State: “₀₀₁” “3” State: “011” “4”State: “010” “5” State: “110” “6” State: “100” “7” State: “000”

In the 133 mapping, the data of each page is determined using thefollowing read voltages.

Lower page read: 4RMiddle page read: 1R, 3R, and 6RUpper page read: 2R, 5R, and 7R

In the 133 mapping, the lower page corresponds to the fast page, whilethe middle page and the upper page correspond to non-fast pages.

<6.2. Data Writes>

In the sixth embodiment, each cell unit CU stores data of three pages insize, and the three pages include just one fast page. Based on thisconfiguration, in the sixth embodiment, the memory area unit MA needs tospread over three independently operable planes PB. In the sixthembodiment, the planes PB0 and PB1 in each memory device MC cannotoperate independently. For this reason, the memory area unit MA needs tospread over three memory devices MC.

To this end, the memory area unit MA according to the sixth embodimentspreads over a plane PB of the memory device MC0, a plane PB of thememory device MC1, and a plane PB of the memory device MC2. The memoryarea unit MA according to the sixth embodiment is referred to as thememory area unit MA4.

FIG. 36 illustrates an example of the memory area unit MA4 and positionswhere page data are written in the memory devices MC according to thesixth embodiment. As illustrated in FIG. 36, the memory area unit MA4 isthe set of the lower, middle, and upper pages of a cell unit CUs0 w in aplane PBw of the memory device MC0, the lower, middle, and upper pagesof a cell unit CUs1 w in a plane PBw of the memory device MC1, and thelower, middle, and upper pages of a cell unit CUs2 w in a plane PBw of amemory device MC2.

Based on such features of the memory area unit MA4, nine pieces of pagedata PG with consecutive logical addresses are stored in a single memoryarea unit MA4. As a specific example, FIG. 36 illustrates the positionswhere nine pieces of page data PG0 to PG8 with consecutive logicaladdresses are written in the memory area unit MA4.

For each of the cases where γ is 0, 3, and 6, the page data PGγ, thepage data PG(γ+1), and the page data PG(γ+2) form a data set.

As illustrated in FIG. 36, the page data PGγ, PG(γ+1), and PG(γ+2) ineach data set are written one by one to the memory devices MC0 to MC2,and in addition, one of the page data PGγ, PG(γ+1), and PG(γ+2) iswritten to a fast page while the remaining two are written to non-fastpages. Also, the page data included in a data set and written to anon-fast page is written to any of the middle and upper pages.Furthermore, the pages to which the page data PG0 to PG8 are written aredetermined such that three data sets are written to the memory area unitMA4. Insofar as writes are performed in this way, the positions wherethe page data PG0 to PG8 are written is not limited to the example inFIG. 36. As an example, the page data written to the non-fast pages arewritten to different one of middle and upper pages.

As illustrated in FIG. 36, the page data PG0 is written to the lowerpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the middle page of the selected cell unit CUs1 wof the memory device MC1. The page data PG2 is written to the upper pageof the selected cell unit CUs2 w of the memory device MC2.

The page data PG3 is written to the lower page of the selected cell unitCUs1 w of the memory device MC1. The page data PG4 is written to themiddle page of the selected cell unit CUs2 w of the memory device MC2.The page data PG5 is written to the upper page of the selected cell unitCUs0 w of the memory device MC0.

The page data PG6 is written to the lower page of the selected cell unitCUs2 w of the memory device MC2. The page data PG7 is written to themiddle page of the selected cell unit CUs0 w of the memory device MC0.The page data PG8 is written to the upper page of the selected cell unitCUs1 w of the memory device MC1.

<6.3. Data Reads>

FIGS. 37 and 38 illustrate the flow of the input and output signal DQduring data reads over time in the memory system 100 according to thesixth embodiment. FIG. 38 illustrates the state following FIG. 37.

As illustrated in FIGS. 37 and 38, a data read from any of the non-fastpages proceeds in parallel with a data read of a fast page (lower page).

To read the data set containing the page data PG0 to PG2, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. The memory device MC0 receives theinstruction and starts a lower page read of the memory device MC0 forobtaining the page data PG0. Next, the memory controller 2 instructs thememory device MC1 to perform a middle page read for the page data PG1,and instructs the memory device MC2 to perform an upper page read forthe page data PG2. The lower page read in the memory device MC0, themiddle page read in the memory device MC1, and the upper page read inthe memory device MC2 proceed in parallel.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the middle page read in the memory device MC1 and the upperpage read in the memory device MC2 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG3 to PG5, and reads the data set containingthe page data PG6 to PG8. For reading any of the data sets, a data readfrom the fast page of each data set is started first, and after that,data reads from the non-fast pages are started. Thus, in each data set,a lower page read, a middle page read, and an upper page read proceed inparallel over the memory devices MC0, MC1, and MC2.

<6.4. Another Example of Mapping>

In the sixth embodiment, other mappings may be used. Such mappingsinclude a 124 mapping. FIG. 39 illustrates a second example of a mappingbetween a threshold voltage distribution of memory cell transistors MTthat store three bits of data per memory cell transistor MT and dataaccording to the sixth embodiment. As illustrated in FIG. 39, in thesecond example, each memory device MC treats each state as having thefollowing three-bit data.

“0” State: “111” “1” State: “011” “2” State: “001” “3” State: “₁₀₁” “4”State: “100” “5” State: “000” “6” State: “010” “7” State: “110”

In the 124 mapping, the data of each page is determined using thefollowing read voltages.

Lower page read: 4RMiddle page read: 2R and 6RUpper page read: 1R, 3R, 5R, and 7R

Also in the 124 mapping, the lower page corresponds to the fast page,while the middle page and the upper page correspond to non-fast pages.

Data writes and reads are the same as for the 133 mapping, thedifference being only in the time taken for the middle page read and theupper page read.

<6.5. Advantages>

According to the sixth embodiment, the memory area unit MA4 spreads overthree memory devices MC, first page data out of a data set containingthree pieces of page data having three consecutive logical addresses iswritten to a fast page (lower page), while the remaining page data arewritten to different pages than the page where the first page data iswritten from among the lower, middle, and upper pages. During reads of adata set written in this way, reads of the page data other than thefirst page data of the data set can proceed while the first page data isbeing output. For this reason, even in the case of storing three bits ofdata per memory cell transistor MT, data can be read and outputefficiently according to the same basic principle as the firstembodiment.

<6.6. Modification>

Like the modification of the third embodiment, the sixth embodiment mayalso be applied to multi-plane operations in which independent operationis unavailable.

In this modification, a memory area unit MA4 a is used. The memory areaunit MA4 a according to a modification of the sixth embodiment spreadsover the planes PB0 and PB1 of the memory device MC0, the planes PB0 andPB1 of the memory device MC1, and the planes PB0 and PB1 of the memorydevice MC2.

FIG. 40 illustrates an example of the memory area unit MA4 a andpositions where page data are written in the memory devices MC accordingto the modification of the sixth embodiment. For each of the cases whereγ is 0, 6, and 12, the page data PGγ, the page data PG(γ+1), the pagedata PG(γ+2), the page data PG(γ+3), the page data PG(γ+4), and the pagedata PG(γ+5) form a data set.

As illustrated in FIG. 40, the page data PG0 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0. The page data PG1 is written to the lower page of theselected cell unit CUs01 in the plane PB1 of the memory device MC0.

The page data PG2 is written to the middle page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG3is written to the middle page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

The page data PG4 is written to the upper page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG5 iswritten to the upper page of the selected cell unit CUs21 in the planePB1 of the memory device MC2.

The page data PG6 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG7 iswritten to the lower page of the selected cell unit CUs11 in the planePE of the memory device MC1.

The page data PG8 is written to the middle page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG9is written to the middle page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG10 is written to the upper page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG11is written to the upper page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

The page data PG12 is written to the lower page of the selected cellunit CUs20 in the plane PB0 of the memory device MC2. The page data PG13is written to the lower page of the selected cell unit CUs21 in theplane PB1 of the memory device MC2.

The page data PG14 is written to the middle page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG15is written to the middle page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0.

The page data PG16 is written to the upper page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG17is written to the upper page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1.

For data reads, the basic principle is the same as data reads accordingto the sixth embodiment, the difference being that pairs of page data PGare read in parallel, like the modification of the fifth embodiment.

The modification may also be applied to the 124 mapping.

Seventh Embodiment

The seventh embodiment resembles the first embodiment and the sixthembodiment. In the seventh embodiment, like the sixth embodiment, eachmemory device MC stores three bits of data per memory cell transistorMT.

The configuration of the memory system 100 and the memory devices MCaccording to the seventh embodiment is the same as that of the firstembodiment.

<7.1. Data Writes>

In the seventh embodiment, like the sixth embodiment, the 133 mapping orthe 124 mapping is used, and the memory area unit MA needs to spreadover three independently operable planes PB. To this end, the memoryarea unit MA according to the seventh embodiment spreads over the planePB0 of the memory device MC0, the plane PB1 of the memory device MC0,and any plane PB (for example, PB0) of the memory device MC1. The memoryarea unit MA according to the seventh embodiment is referred to as thememory area unit MA5.

FIG. 41 illustrates an example of the memory area unit MA5 and positionswhere page data are written in the memory devices MC according to theseventh embodiment. As illustrated in FIG. 41, the memory area unit MA5is the set of the lower, middle, and upper pages of the cell unit CUs00in the plane PB0 of the memory device MC0, the lower, middle, and upperpages of the cell unit CUs01 in the plane PB1 of the memory device MC0,and the lower, middle, and upper pages of the cell unit CUs10 in theplane PB0 for example of the memory device MC1.

The page data PG0 is written to the lower page of the selected cell unitCUs00 in the plane PB0 of the memory device MC0. The page data PG1 iswritten to the middle page of the selected cell unit CUs01 in the planePB1 of the memory device MC0. The page data PG2 is written to the upperpage of the selected cell unit CUs10 in the plane PB0 of the memorydevice MC1.

The page data PG3 is written to the lower page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG4 iswritten to the middle page of the selected cell unit CUs10 in the planePB0 of the memory device MC1. The page data PG5 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0.

The page data PG6 is written to the lower page of the selected cell unitCUs10 in the plane PB0 of the memory device MC1. The page data PG7 iswritten to the middle page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG8 is written to the upperpage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MC0.

<7.2. Data Reads>

Data reads follow the basic principle described for the otherembodiments, and particularly resembles the sixth embodiment. In otherwords, data are read in parallel for each data set, and a data read fromany of the non-fast pages proceeds in parallel with a data read of afast page (lower page). A feature that differs from the sixth embodimentis that the command set for data reads is different on the basis ofthree independent planes PB that store the three pieces of page data PGof a data set spreading over two memory devices MC.

<7.3. Advantages>

According to the seventh embodiment, the memory area unit MA5 spreadsover two memory devices MC, and, like the sixth embodiment, first pagedata out of a data set containing three pieces of page data having threeconsecutive logical addresses is written to a fast page (lower page),while the remaining-page data are written to different pages than thepage where the first page data is written from among the lower, middle,and upper pages. Therefore, like the sixth embodiment, even in the caseof storing three bits of data per memory cell transistor MT, data can beread and output efficiently according to the same basic principle as thefirst embodiment.

<7.4. Modification>

The memory area unit MA may also be formed over six planes PB with threememory devices MC. This modification relates to such an example.

In this modification, a memory area unit MA6 is used. The memory areaunit MA6 spreads over the planes PB0 and PB1 of the memory device MC0,the planes PB0 and PB1 of the memory device MC1, and the planes PB0 andPB1 of the memory device MC2.

FIG. 42 illustrates an example of the memory area unit MA6 and positionswhere page data are written in the memory devices MC according to themodification of the seventh embodiment. As illustrated in FIG. 42, thememory area unit MA6 is the set of the lower, middle, and upper pages ofa cell unit CUs00 in a plane PB0 of a memory device MC0, the lower,middle, and upper pages of a cell unit CUs01 in a plane PB1 of thememory device MC0, the lower, middle, and upper pages of a cell unitCUs10 in a plane PB0 of a memory device MC1, the lower, middle, andupper pages of a cell unit CUs11 in a plane PB1 of the memory deviceMC1, the lower, middle, and upper pages of a cell unit CUs20 in a planePB0 of a memory device MC2, and the lower, middle, and upper pages of acell unit CUs21 in a plane PB1 of the memory device MC2.

The page data PG0 is written to the lower page of the selected cell unitCUs00 in the plane PB0 of the memory device MC0. The page data PG1 iswritten to the middle page of the selected cell unit CUs01 in the planePB1 of the memory device MC0. The page data PG2 is written to the upperpage of the selected cell unit CUs10 in the plane PB0 of the memorydevice MC1.

The page data PG3 is written to the lower page of the selected cell unitCUs11 in the plane PB1 of the memory device MC1. The page data PG4 iswritten to the middle page of the selected cell unit CUs20 in the planePB0 of the memory device MC2. The page data PG5 is written to the upperpage of the selected cell unit CUs21 in the plane PB1 of the memorydevice MC2.

The page data PG6 is written to the lower page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG7 iswritten to the middle page of the selected cell unit CUs10 in the planePB0 of the memory device MC1. The page data PG8 is written to the upperpage of the selected cell unit CUs11 in the plane PB1 of the memorydevice MC1.

The page data PG9 is written to the lower page of the selected cell unitCUs20 in the plane PB0 of the memory device MC2. The page data PG10 iswritten to the middle page of the selected cell unit CUs21 in the planePB1 of the memory device MC2. The page data PG11 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0.

The page data PG12 is written to the lower page of the selected cellunit CUs10 in the plane PB0 of the memory device MC1. The page data PG13is written to the middle page of the selected cell unit CUs11 in theplane PB1 of the memory device MC1. The page data PG14 is written to theupper page of the selected cell unit CUs20 in the plane PB0 of thememory device MC2.

The page data PG15 is written to the lower page of the selected cellunit CUs21 in the plane PB1 of the memory device MC2. The page data PG16is written to the middle page of the selected cell unit CUs00 in theplane PB0 of the memory device MC0. The page data PG17 is written to theupper page of the selected cell unit CUs01 in the plane PB1 of thememory device MC0.

Eighth Embodiment

The eighth embodiment resembles the first embodiment and the sixthembodiment, and relates to an example in which each memory device MCincludes three independently operable planes PB. In the eighthembodiment, like the sixth embodiment, each memory device MC storesthree bits of data per memory cell transistor.

The configuration of the memory system 100 and the memory devices MCaccording to the eighth embodiment is the same as that of the firstembodiment, except that the memory devices MC include three planes PB.Hereinafter, the features that differ from the sixth embodiment will bedescribed mainly.

<8.1. Configuration of Memory Devices>

Each memory device MC includes a plane PB2 in addition to the componentsand connections illustrated in FIG. 3. The plane PB2 is independent fromthe planes PB0 and PB1, and can execute data read, write, and eraseoperations independently. To this end, the plane PB2 includes a memorycell array 13_2, a potential generator 14_2, a driver 15_2, a senseamplifier 16_2, and a row decoder 17_2 (not illustrated). The memorycell array 13_2, the potential generator 14_2, the driver 15_2, thesense amplifier 16_2, and the row decoder 17_2 include the samecomponents and connections as the memory cell array 130, the potentialgenerator 14_0, the driver 15_0, the sense amplifier 16_0, and the rowdecoder 17_0 of the plane PB0, respectively.

<8.2. Data Writes>

In the eighth embodiment, like the sixth embodiment, the 133 mapping orthe 124 mapping is used, and the memory area unit MA needs to spreadover three independently operable planes PB. To this end, the memoryarea unit MA according to the eighth embodiment spreads over the planePB0 of a certain memory device MCw, the plane PB1 of the memory deviceMCw, and the plane PB2 of the memory device MCw. The memory area unit MAaccording to the eighth embodiment is referred to as the memory areaunit MA7.

FIG. 43 illustrates an example of the memory area unit MA7 and positionswhere page data are written in the memory device MC according to theeighth embodiment, and illustrates the memory device MC0 as an example.As illustrated in FIG. 43, the memory area unit MA7 is the set of thelower, middle, and upper pages of the cell unit CUs00 in the plane PB0of the memory device MC0, the lower, middle, and upper pages of the cellunit CUs01 in the plane PB1 of the memory device MC0, and the lower,middle, and upper pages of a cell unit CUs02 in the plane PB2 of thememory device MC0.

The page data PG0 is written to the lower page of the selected cell unitCUs00 in the plane PB0 of the memory device MC0. The page data PG1 iswritten to the middle page of the selected cell unit CUs01 in the planePB1 of the memory device MC0. The page data PG2 is written to the upperpage of the selected cell unit CUs02 in the plane PB2 of the memorydevice MC0.

The page data PG3 is written to the lower page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG4 iswritten to the middle page of the selected cell unit CUs02 in the planePB2 of the memory device MC0. The page data PG5 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0.

The page data PG6 is written to the lower page of the selected cell unitCUs02 in the plane PB2 of the memory device MC0. The page data PG7 iswritten to the middle page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG8 is written to the upperpage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MC0.

<8.3. Data Reads>

Data reads follow the basic principle described for the otherembodiments, and particularly resembles the sixth embodiment. In otherwords, data are read in parallel for each data set, and a data read fromany of the non-fast pages proceeds in parallel with a data read of afast page (lower page). A feature that differs from the sixth embodimentis that the command set for data reads is different on the basis ofthree independent planes PB that store the three pieces of page data ofa data set being included in a single memory device MC.

<8.4. Advantages>

According to the eighth embodiment, the memory area unit MA7 spreadsover three independently operable planes PB in a single memory deviceMC, and, like the sixth embodiment, first page data out of a data setcontaining three pieces of page data having three consecutive logicaladdresses is written to a fast page (lower page), while the remainingpage data are written to different pages than the page where the firstpage data is written from among the lower, middle, and upper pages.Therefore, like the sixth embodiment, even in the case of storing threebits of data per memory cell transistor MT, data can be read and outputefficiently according to the same basic principle as the firstembodiment.

Ninth Embodiment

The ninth embodiment resembles the first embodiment and the sixthembodiment. In the ninth embodiment, like the sixth embodiment, thememory devices MC store three bits of data per memory cell transistor.

The configuration of the memory system 100 and the memory devices MCaccording to the ninth embodiment is the same as that of the sixthembodiment.

<9.1. Mapping>

In the ninth embodiment, a 232 mapping is used. FIG. 44 illustrates anexample of a mapping between eight states of the memory cell transistorsMT in the memory devices MC and three-bit data according to the ninthembodiment. As illustrated in FIG. 44, in the ninth embodiment, thememory devices MC treats each state as having the following three-bitdata.

“0” State: “111” “1” State: “110” “2” State: “100” “3” State: “000” “4”State: “010” “5” State: “011” “6” State: “001” “7” State: “101”

In the 232 mapping, the data of each page is determined using thefollowing read voltages.

Lower page read: 1R and 5RMiddle page read: 2R, 4R, and 6RUpper page read: 3R and 7R

In the 232 mapping, the lower page and the upper page correspond to fastpages, while the middle page corresponds to the non-fast page.

<9.2. Data Writes>

In the ninth embodiment, each cell unit CU stores data of three pages insize, and the three pages include two fast pages. Based on thisconfiguration, in the ninth embodiment, the memory area unit MA needs tospread over three independently operable planes PB. Like the sixthembodiment, the memory area unit MA4 is used.

FIG. 45 illustrates an example of positions where page data are writtenin the memory devices MC according to the ninth embodiment.

As illustrated in FIG. 45, the page data PG0 is written to the upperpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the lower page of the selected cell unit CUs1 wof the memory device MC1. The page data PG2 is written to the middlepage of the selected cell unit CUs2 w of the memory device MC2.

The page data PG3 is written to the upper page of the selected cell unitCUs1 w of the memory device MC1. The page data PG4 is written to thelower page of the selected cell unit CUs2 w of the memory device MC2.The page data PG5 is written to the middle page of the selected cellunit CUs0 w of the memory device MC0.

The page data PG6 is written to the upper page of the selected cell unitCUs2 w of the memory device MC2. The page data PG7 is written to thelower page of the selected cell unit CUs0 w of the memory device MC0.The page data PG8 is written to the middle page of the selected cellunit CUs1 w of the memory device MC1.

The writes in FIG. 45 are an example, are the lower page may also beused as the fast page.

<9.3. Data Reads>

Data reads follow the basic principle described for the otherembodiments, and particularly resembles the sixth embodiment. In otherwords, data is read in parallel for each data set, and a data read fromany of the non-fast pages proceeds in parallel with a data read of afast page (lower or upper page). A feature that differs from the sixthembodiment is that the command set for data reads is different on thebasis of three independent planes PB that store the three pieces of pagedata of a data set extending over three memory devices MC.

<9.4. Advantages>

According to the ninth embodiment, like the sixth embodiment, the memoryarea unit MA4 spreads over three memory devices MC, first page data outof a data set containing three pieces of page data having threeconsecutive logical addresses is written to a fast page, while theremaining page data are written to different pages than the page wherethe first page data is written from among the lower, middle, and upperpages. Therefore, like the sixth embodiment, even in the case of storingthree bits of data per memory cell transistor MT, data can be read andoutput efficiently according to the same basic principle as the firstembodiment.

<9.5. Modification>

Like the modification of the sixth embodiment, the ninth embodiment mayalso be applied to multi-plane operations in which independent operationis unavailable.

10th Embodiment

The 10th embodiment resembles the eighth embodiment and the ninthembodiment, and relates to an example in which each memory device MCincludes three independently operable planes. In the 10th embodiment,like the sixth embodiment, the memory devices MC store three bits ofdata per memory cell transistor.

The configuration of the memory system 100 and the memory devices MCaccording to the 10th embodiment is the same as the eighth embodiment.

<10.1. Data Writing>

In the 10th embodiment, the 232 mapping is used like the ninthembodiment, and the memory area unit MA7 is used like the eighthembodiment.

FIG. 46 illustrates an example of positions where page data are writtenin the memory device MC according to the 10th embodiment, andillustrates the memory device MC0 as an example. As illustrated in FIG.46, the page data PG0 is written to the upper page of the selected cellunit CUs00 in the plane PB0 of the memory device MC0. The page data PG1is written to the lower page of the selected cell unit CUs01 in theplane PB1 of the memory device MC0. The page data PG2 is written to themiddle page of the selected cell unit CUs02 in the plane PB2 of thememory device MC0.

The page data PG3 is written to the upper page of the selected cell unitCUs01 in the plane PB1 of the memory device MC0. The page data PG4 iswritten to the lower page of the selected cell unit CUs02 in the planePB2 of the memory device MC0. The page data PG5 is written to the middlepage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MC0.

The page data PG6 is written to the upper page of the selected cell unitCUs02 in the plane PB2 of the memory device MC0. The page data PG7 iswritten to the lower page of the selected cell unit CUs00 in the planePB0 of the memory device MC0. The page data PG8 is written to the middlepage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MC0.

<10.2. Data Reads>

Data reads follow the basic principle described for the otherembodiments, and particularly resembles the sixth embodiment. In otherwords, data are read in parallel for each data set, and a data read fromany of the non-fast pages proceed in parallel with a data read of a fastpage (upper page). A feature that differs from the sixth embodiment isthat the page read first in the reads of each data set is different.

<10.3. Advantages>

According to the 10th embodiment the memory area unit MA7 spreads overthree independently operable planes PB in a single memory device MC,and, like the sixth embodiment, first page data out of a data setcontaining three pieces of page data having three consecutive logicaladdresses is written to a fast page (upper page), while the remainingpage data are written to different pages than the page where the firstpage data is written from among the lower, middle, and upper pages.Therefore, like the sixth embodiment, even in the case of storing threebits of data per memory cell transistor MT, data can be read and outputefficiently according to the same basic principle as the firstembodiment.

11th Embodiment

The 11th embodiment resembles the third embodiment. In the 11thembodiment, the memory devices MC store two bits of data per memory celltransistor.

The configuration of the memory system 100 and the memory devices MCaccording to the 11th embodiment is the same as that of the thirdembodiment.

<11.1. Mapping>

In the 11th embodiment, a 12 mapping is used. The notation “HI mapping”indicates that H and I read voltages VCGR are used for the lower andupper page reads, respectively.

FIG. 47 illustrates an example of a mapping between four states of thememory cell transistors MT in the memory devices MC and two-bit dataaccording to the 11th embodiment. As illustrated in FIG. 47, in the 11thembodiment, the memory devices MC treat each state as having thefollowing two-bit data.

“0” State: “11” “1” State: “10” “2” State: “00” “3” State: “01”

In the 12 mapping, the data of each page is determined using thefollowing read voltages.

Lower page read: 2RUpper page read: 1R and 3R

In the 12 mapping, the lower page corresponds to the fast page, whilethe upper page corresponds to the non-fast page.

To designate pages with respect to the memory devices MC that storetwo-bit data per memory cell transistor MT like the 11th embodiment, thecommand 01h and the command 02h are used. The command 01h designates thelower page. The command 02h designates the lower page.

<11.2. Data Writes>

In the 11th embodiment, each cell unit CU stores data of two pages insize, and the two pages include just one fast page. Based on thisconfiguration, in the 11th embodiment, the memory area unit MA needs tospread over two independently operable planes PB. In the 11thembodiment, the planes PB0 and PB1 in each memory device MC cannotoperate independently. For this reason, the memory area unit MA needs tospread over two memory devices MC.

To this end, the memory area unit MA according to the 11th embodimentspreads over a plane PB of the memory device MC0 and a plane PB of thememory device MC1. The memory area unit MA according to the 11thembodiment is referred to as the memory area unit MA8.

FIG. 48 illustrates an example of the memory area unit MA8 and positionswhere page data are written in the memory devices MC according to the11th embodiment. As illustrated in FIG. 48, the memory area unit MA8 isthe set of the lower and upper pages of a cell unit CUs0 w in a planePBw of the memory device MC0, and the lower and upper pages of a cellunit CUs1 w in a plane PBw of the memory device MC1.

Based on such features of the memory area unit MA8, four pieces of pagedata with consecutive logical addresses are stored in a single memoryarea unit MA8. As a specific example, FIG. 48 illustrates the positionswhere four pieces of write page data PG0 to PG3 with consecutive logicaladdresses are written in the memory area unit MA8.

For each of the cases where γ is 0 and 2, the page data PGγ and the pagedata PG(γ+1) form a data set.

As illustrated in FIG. 48, the page data PGγ and PG(γ+1) of each dataset are written one by one to the memory devices MC0 and MC1, and inaddition, one of the page data PGγ and PG(γ+1) is written to a fast pagewhile the remaining one is written to a non-fast page.

As illustrated in FIG. 48, the page data PG0 is written to the lowerpage of the selected cell unit CUs0 w of the memory device MC0. The pagedata PG1 is written to the upper page of the selected cell unit CUs1 wof the memory device MC1. The page data PG2 is written to the lower pageof the selected cell unit CUs1 w of the memory device MC1. The page dataPG3 is written to the upper page of the selected cell unit CUs0 w of thememory device MC0.

<11.3. Data Reads>

FIG. 49 illustrates the flow of the input and output signal DQ duringdata reads over time in the memory system 100 according to the 11thembodiment.

As illustrated in FIG. 49, a data read from any of the non-fast pagesproceeds in parallel with a data read of a fast page (lower page).

To read the data set containing the page data PG0 and PG1, the memorycontroller 2 first instructs the memory device MC0 to read the page dataPG0 stored in the fast page. The memory device MC0 receives theinstruction and starts a lower page read of the memory device MC0 forobtaining the page data PG0. Next, the memory controller 2 instructs thememory device MC1 to perform an upper page read for the page data PG1.The lower page read in the memory device MC0 and the upper page read inthe memory device MC1 proceed in parallel.

When the read of the page data PG0 is completed, the memory device MC0outputs the page data PG0 in accordance with the instruction from thememory controller 2. While the memory device MC0 is outputting the pagedata PG0, the upper page read in the memory device MC1 can proceed.

Thereafter, the memory controller 2 similarly reads the data setcontaining the page data PG2 and PG3. For reading any of the data sets,a data read from the fast page of each data set is started first, andafter that, data reads from the non-fast pages are started. Thus, ineach data set, a lower page read and an upper page read proceed inparallel over the memory devices MC0 and MC1.

<11.4. Advantages>

According to the 11th embodiment, the memory area unit MA8 spreads overtwo memory devices MC, first page data out of a data set containing twopieces of page data having two consecutive logical addresses is writtento a fast page, while the remaining page data is written to a non-fastpage. During reads of a data set written in this way, a read of the pagedata PG other than the first page data of the data set can proceed whilethe first page data is being output. For this reason, even in the caseof storing two bits of data per memory cell transistor MT, data can beread and output efficiently according to the same basic principle as thefirst embodiment.

<11.5. Modification>

The 11th embodiment may also be applied to independently operable planesPB0 and PB1 in a single memory device MC. In other words, the memorydevice MC has the same configuration as the first embodiment, the memoryarea unit MA spreads over the planes PB0 and PB1 of a single memorydevice MC0 for example, and is the set of the lower and upper pages ofthe plane PB0 and the lower and upper pages of the plane PB1.

12th Embodiment

The 12th embodiment relates to another configuration for achieving datawrites according to the 11th embodiment. Hereinafter, the features thatdiffer from the 11th embodiment will be described mainly.

The configuration of the memory system 100 according to the 12thembodiment is the same as the first embodiment.

<12.1. Configuration of Memory Devices>

FIG. 50 illustrates functional blocks of the memory devices MC accordingto the 12th embodiment. As illustrated in FIG. 50, each memory device MCincludes an address converter 18 in addition to the components andconnections according to the first embodiment (FIG. 3). The memorydevices MC according to the 12th embodiment may be referred to as thememory devices MCb in some cases.

The address converter 18 receives an address signal from the input andoutput circuit 11, and converts a certain portion of the address signal,namely the portion indicating the address for a certain element, to adifferent address according to a predetermined rule. The portions otherthan the portion to be converted are output unchanged by the addressconverter 18. The output from the address converter 18 is supplied tocomponents such as the sequencer 12, the row decoder 17, and the senseamplifier 16.

FIG. 51 illustrates components and connections in the address converter18 according to the 12th embodiment. As illustrated in FIG. 51, theaddress converter 18 includes selectors S1 and S2.

Each of the selectors S1 and S2 includes a first input node, a secondinput node, a control input node, and an output node. Each of the firstinput node and the second input node is associated with a one-bit value.The first input node is associated with “0”, and the second input nodeis associated with “1”. Hereinafter, the first input node may bereferred to as the “0” input node, while the second input node may bereferred to as the “1” input node in some cases.

Each of the selectors S1 and S2 receives a signal CHIP_ADD<0> at thecontrol input node, where <0> indicates that the signal of the precedingname has one bit (the “0th” bit). The signal CHIP_ADD<0> has theidentification (ID) of the memory device MC that includes the addressconverter 18, or in other words, a value based on a unique number thatspecifies one from among all of the memory devices MC included in thememory system 100. For example, the signal CHIP_ADD<0> has the value “0”in the memory device MC0 and the signal CHIP_ADD<0> has the value “1” inthe memory device MC1.

The selector S1 receives a signal Lower_SEL_pre at the “0” input node.The signal Lower_SEL_pre is supplied from the input and output circuit11 for example, and is asserted when the command 01h, which designatesthe lower page, is received by the memory device MC. The signalLower_SEL_pre is used to generate a signal informing the sequencer 12 ofthe page targeted by the process instructed by the command set followingthe command 01h, or in other words the command set associated with thecommand 01h. In other words, when the command 01h is received, a signaldesignating the page targeted by the command set associated with thecommand 01h is generated, and the generated signal is supplied to thesequencer 12.

The selector S1 receives a signal Upper_SEL_pre at the “1” input node.The signal Upper_SEL_pre is supplied from the input and output circuit11 for example, and is asserted when the command 02h, which designatesthe upper page, is received by the memory device MC. The signalUpper_SEL_pre is used to generate a signal informing the sequencer 12 ofthe page targeted by the process instructed by the command set followingthe command 02h, or in other words the command set associated with thecommand 02h. In other words, when the command 02h is received, a signaldesignating the page targeted by the command set associated with thecommand 02h is generated, and the generated signal is supplied to thesequencer 12.

Of the “0” input node and the “1” input node, the selector S1 outputsthe one associated with the same value as the value of the signalreceived by the control input node as a signal Lower_SEL. Specifically,the selector S1 outputs the signal received by the “0” input node whilea “0” value signal is being received at the control input node, andoutputs the signal received by the “1” input node while a “1” valuesignal is being received at the control input node. The signal Lower_SELis supplied to the sequencer 12 and informs the sequencer 12 of thedesignation of the lower page. Using the signal Lower_SEL, the sequencer12 recognizes that the lower page is the target of the command setassociated with the page designation command (01h or 02h) that serves asthe basis for generating the signal Lower_SEL.

The selector S2 receives the signal Upper_SEL_pre at the “0” input node,and receives the signal Lower_SEL_pre at the “1” input node. Of the “0”input node and the “1” input node, the selector S2 outputs the oneassociated with the same value as the value of the signal received bythe control input node as a signal Upper_SEL. Specifically, the selectorS2 outputs the signal received by the “0” input node while a “0” valuesignal is being received at the control input node, and outputs thesignal received by the “1” input node while a “1” value signal is beingreceived at the control input node. The signal Upper_SEL is supplied tothe sequencer 12 and informs the sequencer 12 of the designation of theupper page. Using the signal Upper_SEL, the sequencer 12 recognizes thatthe upper page is the target of the command set associated with the pagedesignation command (01h or 02h) that serves as the basis for generatingthe signal Upper_SEL.

FIG. 52 illustrates an example of a state of the address converter 18according to the 12th embodiment. In particular, FIG. 52 illustrates theaddress converter 18 in the memory device MC1. As illustrated in FIG.52, because the address converter 18 is in the memory device MC1, thesignal CHIP_ADD<0> has the value “1” (has a high level). For thisreason, as indicated by the bold lines, each of the selectors S1 and S2couples its own “1” input node to its own output node. Accordingly, theinterconnect transmitting the signal Lower_SEL_pre is coupled to theoutput node of the selector S2, and the signal Lower_SEL_pre isconverted to the signal Upper_SEL. Also, the interconnect transmittingthe signal Upper_SEL_pre is coupled to the output node of the selectorS1, and the signal Upper_SEL_pre is converted to the signal Lower_SEL.

According to such conversion, when the command 01h designating the lowerpage is received by the memory device MC1, the sequencer 12 is informedthat the target of the command set following the command 01h is theupper page. When the command 02h designating the upper page is receivedby the memory device MC1, the sequencer 12 is informed that the targetof the command set following the command 02h is the lower page.

Note that the address converter 18 of the memory device MC0 receives thesignal CHIP_ADD<0> having the value “0” (having a low level). For thisreason, the signal Lower_SEL has the same logic level as the signalLower_SEL_pre, and the signal Upper_SEL has the same logic level as thesignal Upper_SEL_pre. Accordingly, when the command 01h designating thelower page is received by the memory device MC0, the sequencer 12 isinformed that the target of the command set following the command 01h isthe lower page. When the command 02h designating the upper page isreceived by the memory device MC0, the sequencer 12 is informed that thetarget of the command set following the command 02h is the upper page.

<12.2. Data Writes>

FIG. 53 illustrates a flow of the input and output signal DQ for datawrites in the memory system according to the 12th embodiment. To writedata to the memory devices MC0 and MC1 as illustrated in FIG. 48, thememory controller 2 transmits command sets and the page data PG0 to PG3to the memory devices MC0 and MC1 as illustrated in FIG. 53.

First, to instruct the memory device MC0 to write the page data PG0, thememory controller 2 transmits the page data PG0 and a command setinstructing the memory device MC0 to write the page data PG0 to thelower page of a selected cell unit CUs0 w. For this purpose, the memorycontroller 2 transmits the command 01h, the command 80h, an address Adddesignating the selected cell unit CUs0 w, the page data PG0, and thecommand 1Ah, in that order, for example. When the command set and thepage data PG0 are received by the memory device MC0, the sequencer 12recognizes an instruction to write the page data PG0 to the lower pageof the selected cell unit CUs0 w of the memory device MC0.

To instruct the memory device MC1 to write the page data PG1, the memorycontroller 2 transmits the page data PG1 and a command set instructingthe memory device MC1 to write the page data PG1 to the lower page of acertain selected cell unit CUs1 w. For this purpose, the memorycontroller 2 transmits the command 01h, the command 80h, an address Adddesignating the selected cell unit CUs1 w, the page data PG1, and thecommand 1Ah, in that order, for example. When the command set and thepage data PG1 are received by the memory device MC1, the designation ofthe lower page by the command 01h is converted to a designation of theupper page by the address converter 18. Accordingly, the sequencer 12recognizes an instruction to write the page data PG1 to the upper pageof the selected cell unit CUs1 w of the memory device MC1.

To instruct the memory device MC1 to write the page data PG2, the memorycontroller 2 transmits the page data PG2 and a command set instructingthe memory device MC1 to write the page data PG2 to the upper page ofthe selected cell unit CUs1 w. For this purpose, the memory controller 2transmits the command 02h, the command 80h, an address Add designatingthe selected cell unit CUs1 w, the page data PG2, and the command 10h,in that order, for example. When the command set and the page data PG2are received by the memory device MC1, the designation of the upper pageby the command 02h is converted to a designation of the lower page bythe address converter 18. Accordingly, the sequencer 12 recognizes aninstruction to write the page data PG2 to the lower page of the selectedcell unit CUs1 w of the memory device MC1.

To instruct the memory device MC0 to write the page data PG3, the memorycontroller 2 transmits the page data PG3 and a command set instructingthe memory device MC0 to write the page data PG3 to the upper page ofthe selected cell unit CUs0 w. For this purpose, the memory controller 2transmits the command 02h, the command 80h, an address Add designatingthe selected cell unit CUs0 w, the page data PG3, and the command 10h,in that order, for example. When the command set and the page data PG3are received by the memory device MC0, the sequencer 12 recognizes aninstruction to write the page data PG3 to the upper page of the selectedcell unit CUs0 w of the memory device MC0.

The transmission of commands as illustrated in FIG. 53 means that thememory controller 2 recognizes that the page data PG0 to PG3 have beenwritten to the positions illustrated in FIG. 54. In other words, thememory controller 2 recognizes that the page data PG0 has been writtento the lower page of the selected cell unit CUs0 w of the memory deviceMC0, the page data PG1 has been written to the lower page of theselected cell unit CUs1 w of the memory device MC1, the page data PG2has been written to the upper page of the selected cell unit CUs1 w ofthe memory device MC1, and the page data PG3 has been written to theupper page of the selected cell unit CUs0 w of the memory device MC0.The address conversion table 221 also indicates such correspondencesbetween the page data PG and the physical addresses.

On the other hand, by the transmission of the commands and the page dataPG as illustrated in FIG. 53, the page data PG0 to PG3 are actuallywritten in the memory devices MC0 and MC1 as illustrated in FIG. 48.

<12.3. Data Reads>

FIG. 55 illustrates the flow of the input and output signal DQ duringdata reads over time in the memory system 100 according to the 12thembodiment. It should be noted that the memory controller 2 recognizesthat the positions where the page data PG0 to PG3 are written are likein FIG. 54.

As illustrated in FIG. 55, the memory controller 2 reads the page dataPG0 and PG1 in parallel. For this purpose, first, the memory controller2 transmits a command set instructing the memory device MC0 to perform adata read from the lower page of the selected cell unit CUs0 w. When thecommand set is received by the memory device MC0, the memory device MC0obtains the page data PG0 stored in the lower page of the selected cellunit CUs0 w.

Next, the memory controller 2 transmits a command set instructing thememory device MC1 to perform a data read from the lower page of theselected cell unit CUs1 w. When the command set is received by thememory device MC1, the designation of the lower page by the command 01his converted to a designation of the upper page by the address converter18. Accordingly, the memory device MC1 obtains the page data PG1 storedin the upper page of the selected cell unit CUs1 w.

Next, the memory controller 2 reads the page data PG2 and PG3 inparallel. For this purpose, first, the memory controller 2 transmits acommand set instructing the memory device MC1 to perform a data readfrom the upper page of the selected cell unit CUs1 w. When the commandset is received by the memory device MC1, the designation of the upperpage by the command 02h is converted to a designation of the lower pageby the address converter 18. Accordingly, the memory device MC1 obtainsthe page data PG2 stored in the lower page of the selected cell unitCUs1 w.

Next, the memory controller 2 transmits a command set instructing thememory device MC0 to perform a data read from the upper page of theselected cell unit CUs0 w. When the command set is received by thememory device MC0, the memory device MC0 obtains the page data PG2stored in the upper page of the selected cell unit CUs0 w.

<12.4. Advantages>

In cases where the 12th embodiment is not used, writes of the page dataPG as illustrated in FIG. 48 according to the 11th embodiment typicallyrequires the transmission of command sets and page data according to asequence as illustrated in FIG. 56. In other words, the memory device MCand the page where the page data PG actually is to be written aredesignated. For example, the command set for writing the page data PG1designates the upper page, while the command set for writing the pagedata PG2 designates the lower page. However, such a sequence has littleregularity, and is not arranged well sequentially, such as writing datato the lower pages of the memory devices MC0 and MC1, and then writingdata to the upper pages of the memory devices MC0 and MC1, for example.

According to the 12th embodiment, the transmission of the command setsfor writing data sets as illustrated in the 11th embodiment is highlyregular. In other words, for example, the writes of all data specifyingthe lower pages is complete, and then the writesg of data designatingthe upper pages can occur. Even with such command transmission, data iswritten as illustrated in the 11th embodiment. For this reason, theinstructions for data writes by the memory controller 2 are simple, andthe processing load on the memory controller 2 is light.

<12.5. Modification>

The conversion of designated pages by the address converter 18 or 19like in the 12th embodiment is also applicable to embodiments other thanthe third and 11th embodiments.

13th Embodiment

The 13th embodiment relates to another configuration for achieving datawrites according to the third embodiment. Hereinafter, the features thatdiffer from the third embodiment will be described mainly.

The configuration of the memory system 100 according to the 13thembodiment is the same as the first embodiment.

The description below relates to an example of a configuration forachieving the writes illustrated in FIG. 24 from among the variousspecific examples of data writes according to the third embodiment.Persons skilled in the art are capable of using the principles describedbelow to design a configuration for achieving another example of datawrites (for example, FIG. 21) according to the third embodiment.

<13.1. Configuration of Memory Devices>

FIG. 57 illustrates components and connections in the memory devicesaccording to a 13th embodiment. As illustrated in FIG. 57, each memorydevice MC includes an address converter 19 in addition to the componentsand connections according to the first embodiment (FIG. 3). The memorydevices MC according to the 13th embodiment may be referred to as thememory devices MCc in some cases.

The address converter 19 receives an address signal from the input andoutput circuit 11, and converts a certain portion of the address signal,namely the portion indicating the address for a certain element, to adifferent address according to a predetermined rule. The portions otherthan the portion to be converted are output unchanged by the addressconverter 19. The output from the address converter 19 is supplied tocomponents such as the sequencer 12, the row decoder 17, and the senseamplifier 16.

FIG. 58 illustrates components and connections in the address converter19 according to the 13th embodiment. As illustrated in FIG. 58, theaddress converter 19 includes selectors S11, S12, S13, and S14.

Each of the selectors S11 to S14 includes a first input node, a secondinput node, a third input node, a fourth input node, a control inputnode, and an output node. Each of the first input node to the fourthinput node is associated with a two-bit value. The first input node isassociated with “10”. The second input node is associated with “11”. Thethird input node is associated with “00”. The fourth input node isassociated with “01”. Hereinafter, the first input node may be referredto as the “10” input node, the second input node may be referred to asthe “11” input node, the third input node may be referred to as the “00”input node, and the fourth input node may be referred to as the “01”input node.

Each of the selectors S1 to S14 receives a signal CHIP_ADD<1:0> at thecontrol input node, where the signal CHIP_ADD<1:0> has a value based onthe ID of the memory device MC that includes the address converter 19.For example, the signal CHIP_ADD<1:0> has the value “00” in the memorydevice MC0, has the value “01” in the memory device MC1, has the value“10” in the memory device MC2, and has the value “11” in the memorydevice MC3.

The selector S11 receives a signal Lower_SEL_pre at the “10” input node.

The selector S11 receives a signal Middle_SEL_pre at the “11” inputnode. The signal Middle_SEL_pre is supplied from the input and outputcircuit 11 for example, and is asserted when the command 02h, whichdesignates the middle page, is received by the memory device MC. Thesignal Middle_SEL_pre is used to generate a signal informing thesequencer 12 of the page targeted by the process instructed by thecommand set following the command 02h, or in other words the command setassociated with the command 02h. In other words, when the command 02h isreceived, a signal designating the page targeted by the command setassociated with the command 02h is generated, and the generated signalis supplied to the sequencer 12.

The selector S11 receives a signal Upper_SEL_pre at the “00” input node.The signal Upper_SEL_pre is supplied from the input and output circuit11 for example, and is asserted when the command 03h, which designatesthe upper page, is received by the memory device MC. The signalUpper_SEL_pre is used to generate a signal informing the sequencer 12 ofthe page targeted by the process instructed by the command set followingthe command 03h, or in other words the command set associated with thecommand 03h. In other words, when the command 03h is received, a signaldesignating the page targeted by the command set associated with thecommand 03h is generated, and the generated signal is supplied to thesequencer 12.

The selector S11 receives a signal Top_SEL_pre at the “01” input node.The signal Top_SEL_pre is supplied from the input and output circuit 11for example, and is asserted when a command 04h, which designates thetop page, is received by the memory device MC. The signal Top_SEL_pre isused to generate a signal informing the sequencer 12 of the pagetargeted by the process indicated by the command set following thecommand 04h, or in other words the command set associated with thecommand 04h. In other words, when the command 04h is received, a signaldesignating the page targeted by the command set associated with thecommand 04h is generated, and the generated signal is supplied to thesequencer 12.

Of the “10” input node, the “11” input node, the “00” input node, andthe “01” input node, the selector S11 outputs the one associated withthe bit sequence having the same value as the value of the signalreceived by the control input node as the signal Lower_SEL.Specifically, while a “10” value signal is being received at the controlinput node, the selector S1 outputs the signal received by the “10”input node. While a “11” value signal is being received at the controlinput node, the selector S11 outputs the signal received by the “11”input node. While a “00” value signal is being received at the controlinput node, the selector S11 outputs the signal received by the “00”input node. While a “01” value signal is being received at the controlinput node, the selector S11 outputs the signal received by the “01”input node.

The selector S12 receives the signal Top_SEL_pre at the “10” input node,the signal Lower_SEL_pre at the “11” input node, the signalMiddle_SEL_pre at the “00” input node, and the signal Upper_SEL_pre atthe “01” input node. In a similar manner as the selector S11, of the“10” input node, the “11” input node, the “00” input node, and the “01”input node, the selector S12 outputs the one associated with the bitsequence having the same value as the value of the signal received bythe control input node as the signal Middle_SEL. The signal Middle_SELis supplied to the sequencer 12 and informs the sequencer 12 of thedesignation of the middle page. Using the signal Middle_SEL, thesequencer 12 recognizes that the middle page is the target of thecommand set associated with the page designation command (01h, 02h, 03h,or 04h) that serves as the basis for generating the signal Middle_SEL.

The selector S13 receives the signal Upper_SEL_pre at the “10” inputnode, the signal Top_SEL_pre at the “11” input node, the signalLower_SEL_pre at the “00” input node, and the signal Middle_SEL_pre atthe “01” input node. In a similar manner as the selector 811, of the“10” input node, the “11” input node, the “00” input node, and the “01”input node, the selector S13 outputs the one associated with the bitsequence having the same value as the value of the signal received bythe control input node as the signal Upper_SEL.

The selector 814 receives the signal Middle_SEL_pre at the “10” inputnode, the signal Upper_SEL_pre at the “11” input node, the signalTop_SEL_pre at the “00” input node, and the signal Lower_SEL_pre at the“01” input node. In a similar manner as the selector S11, of the “10”input node, the “11” input node, the “00” input node, and the “01” inputnode, the selector S14 outputs the one associated with the bit sequencehaving the same value as the value of the signal received by the controlinput node as the signal Top_SEL. The signal Top_SEL is supplied to thesequencer 12 and informs the sequencer 12 of the designation of the toppage. Using the signal Top_SEL, the sequencer 12 recognizes that the toppage is the target of the command set associated with the pagedesignation command (01h, 02h, 03h, or 04h) that serves as the basis forgenerating the signal Top_SEL.

FIG. 59 illustrates an example of a state of the address converter 19according to the 13th embodiment. In particular, FIG. 59 illustrates theaddress converter 19 in the memory device MC0. As illustrated in FIG.59, because the address converter 19 is in the memory device MC0, thesignal CHIP_ADD<1:0> has the value “00” (each bit is at a low level).For this reason, as indicated by the bold lines, each of the selectorsS1 to S4 couples its own “00” input node to its own output node.Accordingly, the interconnect transmitting the signal Lower_SEL_pre iscoupled to the output node of the selector S13, and the signalLower_SEL_pre is converted to the signal Upper_SEL. The interconnecttransmitting the signal Middle_SEL_pre is coupled to the output node ofthe selector S12, and the signal Middle_SEL_pre is converted to thesignal Middle_SEL. The interconnect transmitting the signalUpper_SEL_pre is coupled to the output node of the selector S11, and thesignal Upper_SEL_pre is converted to the signal Lower_SEL. Theinterconnect transmitting the signal Top_SEL_pre is coupled to theoutput node of the selector S14, and the signal Top_SEL_pre is convertedto the signal Top_SEL.

According to such conversion, when the command 01h designating the lowerpage is received by the memory device MC0, the sequencer 12 is informedthat the target of the command set following the command 01h is theupper page. When the command 03h designating the upper page is receivedby the memory device MC0, the sequencer 12 is informed that the targetof the command set following the command 03h is the lower page.

On the other hand, when the command 02h designating the upper page isreceived by the memory device MC0, the sequencer 12 is informed that thetarget of the command set following the command 02h is the middle page.When the command 04h designating the top page is received by the memorydevice MC0, the sequencer 12 is informed that the target of the commandset following the command 04h is the top page.

In the address converter 19 of the memory devices MC1, MC2, and MC3,conversion is performed in a different form from the address converter19 of the memory device MC0 according to the same basic principle as thebasic principle in the address converter 19 of the memory device MC0.

In the address converter 19 of the memory device MC1, the signalLower_SEL_pre is converted to the signal Top_SEL. The signalMiddle_SEL_pre is converted to the signal Upper_SEL. The signalUpper_SEL_pre is converted to the signal Middle_SEL. The signalTop_SEL_pre is converted to the signal Lower_SEL.

In the address converter 19 of the memory device MC2, the signalLower_SEL_pre is converted to the signal Lower_SEL. The signalMiddle_SEL_pre is converted to the signal Top_SEL. The signalUpper_SEL_pre is converted to the signal Upper_SEL. The signalTop_SEL_pre is converted to the signal Middle_SEL.

In the address converter 19 of the memory device MC3, the signalLower_SEL_pre is converted to the signal Middle_SEL. The signalMiddle_SEL_pre is converted to the signal Lower_SEL. The signalUpper_SEL_pre is converted to the signal Top_SEL. The signal Top_SEL_preis converted to the signal Upper_SEL.

<13.2. Data Writes>

FIGS. 60 and 61 illustrate the flow of the input and output signal DOfor writes in the memory system 100 according to the 13th embodiment.FIG. 61 illustrates the state following FIG. 60.

To write data to the memory devices MC0 to MC3 as illustrated in FIGS.60 and 61, the memory controller 2 transmits command sets and the pagedata PG0 to PG15 to the memory devices MC0 to MC3 as illustrated inFIGS. 60 and 61.

First, to instruct the memory device MC0 to write the page data PG0, thememory controller 2 transmits the page data PG0 and a command setinstructing the memory device MC0 to write the page data PG0 to thelower page of a selected cell unit CUs0 w. For this purpose, the memorycontroller 2 transmits the command 01h, the command 80h, an address Adddesignating the selected cell unit CUs0 w, the page data PG0, and thecommand 1Ah, in that order, for example. When the command set and thepage data PG0 are received by the memory device MC0, the designation ofthe lower page by the command 01h is converted to a designation of theupper page by the address converter 19. Accordingly, the sequencer 12recognizes an instruction to write the page data PG0 to the upper pageof the selected cell unit CUs0 w of the memory device MC0.

To instruct the memory device MC1 to write the page data PG1, the memorycontroller 2 transmits the page data PG1 and a command set instructingthe memory device MC1 to write the page data PG1 to the lower page of aselected cell unit CUs1 w. For this purpose, the memory controller 2transmits the command 01h, the command 80h, an address Add designatingthe selected cell unit CUs1 w, the page data PG1, and the command 1Ah,in that order, for example. When the command set and the page data PG1are received by the memory device MC1, the designation of the lower pageby the command 01h is converted to a designation of the top page by theaddress converter 19. Accordingly, the sequencer 12 recognizes aninstruction to write the page data PG1 to the top page of the selectedcell unit CUs1 w of the memory device MC1.

To instruct the memory device MC2 to write the page data PG2, the memorycontroller 2 transmits the page data PG2 and a command set instructingthe memory device MC2 to write the page data PG2 to the lower page of aselected cell unit CUs2 w. For this purpose, the memory controller 2transmits the command 01h, the command 80h, an address Add designatingthe selected cell unit CUs2 w, the page data PG2, and the command 1Ah,in that order, for example. When the command set and the page data PG2are received by the memory device MC2, the designation of the lower pageby the command 01h is informed as a designation of the lower page by theaddress converter 19. Accordingly, the sequencer 12 recognizes aninstruction to write the page data PG2 to the lower page of the selectedcell unit CUs2 w of the memory device MC2.

To instruct the memory device MC3 to write the page data PG3, the memorycontroller 2 transmits the page data PG3 and a command set instructingthe memory device MC3 to write the page data PG3 to the lower page of aselected cell unit CUs3 w. For this purpose, the memory controller 2transmits the command 01h, the command 80h, an address Add designatingthe selected cell unit CUs3 w, the page data PG3, and the command 1Ah,in that order, for example. When the command set and the page data PG3are received by the memory device MC3, the designation of the lower pageby the command 01h is converted to a designation of the middle page bythe address converter 19. Accordingly, the sequencer 12 recognizes aninstruction to write the page data PG3 to the middle page of theselected cell unit CUs3 w of the memory device MC3.

Thereafter, in a similar manner, instructions for writing the page dataPG4 to PG15 are issued by the memory controller 2. The command sets forwriting the page data PG4 to PG7 include the command 02h, the command80h, the address Add, the page data PG, and the command 1Ah. In thememory device MC1, the designation of the middle page by the command 02his converted to a designation of the upper page by the address converter19. In the memory device MC2, the designation of the middle page by thecommand 02h is converted to a designation of the top page by the addressconverter 19. In the memory device MC3, the designation of the middlepage by the command 02h is converted to a designation of the lower pageby the address converter 19. In the memory device MC0, the designationof the middle page by the command 02h is maintained as a designation ofthe middle page.

The command sets for writing the page data PG8 to PG11 include thecommand 03h, the command 80h, the address Add, the page data PG, and thecommand 1Ah. In the memory device MC2, the designation of the upper pageby the command 03h is maintained as a designation of the upper page. Inthe memory device MC3, the designation of the upper page by the command03h is converted to a designation of the top page by the addressconverter 19. In the memory device MC0, the designation of the upperpage by the command 03h is converted to a designation of the lower pageby the address converter 19. In the memory device MC1, the designationof the upper page by the command 03h is converted to a designation ofthe middle page by the address converter 19.

The command sets for writing the page data PG12 to PG15 include thecommand 04h, the command 80h, the address Add, the page data PG, and thecommand 10h. In the memory device MC3, the designation of the top pageby the command 04h is converted to a designation of the upper page bythe address converter 19. In the memory device MC0, the designation ofthe middle page by the command 04h is maintained as a designation of thetop page. In the memory device MC1, the designation of the top page bythe command 04h is converted to a designation of the lower page by theaddress converter 19. In the memory device MC2, the designation of thetop page by the command 04h is converted to a designation of the middlepage by the address converter 19.

The transmission of commands as illustrated in FIGS. 60 and 61 meansthat the memory controller 2 recognizes that the page data PG0 to PG15have been written as illustrated in FIG. 62. In other words, the memorycontroller 2 recognizes that the page data PG0 has been written to thelower page of the selected cell unit CUs0 w of the memory device MC0,the page data PG1 has been written to the lower page of the selectedcell unit CUs1 w of the memory device MC1, the page data PG2 has beenwritten to the lower page of the selected cell unit CUs2 w of the memorydevice MC2, and the page data PG3 has been written to the lower page ofthe selected cell unit CUs3 w of the memory device MC3.

The memory controller 2 recognizes that the page data PG4 has beenwritten to the middle page of the selected cell unit CUs1 w of thememory device MC1, the page data PG5 has been written to the middle pageof the selected cell unit CUs2 w of the memory device MC2, the page dataPG6 has been written to the middle page of the selected cell unit CUs3 wof the memory device MC3, and the page data PG7 has been written to themiddle page of the selected cell unit CUs0 w of the memory device MC0.

The memory controller 2 recognizes that the page data PG8 has beenwritten to the upper page of the selected cell unit CUs2 w of the memorydevice MC2, the page data PG9 has been written to the upper page of theselected cell unit CUs3 w of the memory device MC3, the page data PG10has been written to the upper page of the selected cell unit CUs0 w ofthe memory device MC0, and the page data PG11 has been written to theupper page of the selected cell unit CUs1 w of the memory device MC1.

The memory controller 2 recognizes that the page data PG12 has beenwritten to the top page of the selected cell unit CUs3 w of the memorydevice MC3, the page data PG13 has been written to the top page of theselected cell unit CUs0 w of the memory device MC0, the page data PG14has been written to the top page of the selected cell unit CUs1 w of thememory device MC1, and the page data PG15 has been written to the toppage of the selected cell unit CUs2 w of the memory device MC2.

The address conversion table 221 also indicates such correspondencesbetween the page data PG and the physical addresses.

On the other hand, by the transmission of the commands and the page dataPG as illustrated in FIGS. 60 and 61, the page data PG0 to PG15 areactually written in the memory devices MC0 to MC3 as illustrated in FIG.24.

<13.3. Data Reads>

FIGS. 63 and 64 illustrate the flow of the input and output signal DQduring data reads over time in the memory system 100 according to the13th embodiment. FIG. 64 illustrates the state following FIG. 63. Itshould be noted that the memory controller 2 recognizes that thepositions where the page data PG0 to PG15 are written are like in FIG.24.

As illustrated in FIGS. 63 and 64, the memory controller 2 reads thepage data PG0 to PG3 in parallel. For this purpose, first, the memorycontroller 2 transmits a command set instructing the memory device MC0to perform a data read from the lower page of the selected cell unitCUs0 w. When the command set is received by the memory device MC0, thedesignation of the lower page by the command 01h is converted to adesignation of the upper page by the address converter 19. Accordingly,the memory device MC0 obtains the page data PG0 stored in the upper pageof the selected cell unit CUs0 w.

The memory controller 2 transmits a command set instructing the memorydevice MC1 to perform a data read from the lower page of the selectedcell unit CUs1 w. When the command set is received by the memory deviceMC1, the designation of the lower page by the command 01h is convertedto a designation of the top page by the address converter 19.Accordingly, the memory device MC1 obtains the page data PG1 stored inthe top page of the selected cell unit CUs1 w.

The memory controller 2 transmits a command set instructing the memorydevice MC2 to perform a data read from the lower page of the selectedcell unit CUs2 w. When the command set is received by the memory deviceMC2, the designation of the lower page by the command 01h is maintainedas a designation of the lower page by the address converter 19.Accordingly, the memory device MC2 obtains the page data PG2 stored inthe lower page of the selected cell unit CUs2 w.

The memory controller 2 transmits a command set instructing the memorydevice MC3 to perform a data read from the lower page of the selectedcell unit CUs3 w. When the command set is received by the memory deviceMC3, the designation of the lower page by the command 01h is convertedto a designation of the middle page by the address converter 19.Accordingly, the memory device MC3 obtains the page data PG3 stored inthe middle page of the selected cell unit CUs3 w.

Thereafter, in a similar manner, instructions for reading the page dataPG4 to PG15 are issued by the memory controller 2. The command sets forreading the page data PG4 to PG7 include the command 02h, the command00h, the address Add, and the command 30h. The designation of the middlepage by the command 02h is converted as described for data writes. Forthis reason, an upper page read in the memory device MC1, a top pageread in the memory device MC2, a lower page read in the memory deviceMC3, and a middle page read in the memory device MC0 are performed. As aresult, the page data PG4 to PG7 are obtained.

The command sets for reading the page data PG8 to PG11 include thecommand 03h, the command 00h, the address Add, and the command 30h. Thedesignation of the upper page by the command 03h is converted asdescribed for data writes. For this reason, an upper page read in thememory device MC2, a top page read in the memory device MC3, a lowerpage read in the memory device MC0, and a middle page read in the memorydevice MC1 are performed. As a result, the page data PG8 to PG11 areobtained.

The command sets for reading the page data PG12 to PG15 include thecommand 04h, the command 00h, the address Add, and the command 30h. Thedesignation of the top page by the command 04h is converted as describedfor data writes. For this reason, an upper page read in the memorydevice MC3, a top page read in the memory device MC0, a lower page readin the memory device MC1, and a middle page read in the memory deviceMC2 are performed. As a result, the data written as the page data PG12to PG15 is obtained.

<13.4. Advantages>

In cases where the 13th embodiment is not used, writes of the page dataPG as illustrated in FIG. 24 according to the 13th embodiment typicallyrequires the transmission of command sets and page data according to asequence as illustrated in FIG. 65. In other words, the memory device MCand the page where the page data PG actually is to be written aredesignated. For example, the command set for writing the page data PG0designates the upper page of the memory device MC0, the command set forwriting the page data PG1 designates the top page of the memory deviceMC1, the command set for writing the page data PG2 designates the lowerpage of the memory device MC2, and the command set for writing the pagedata PG3 designates the middle page of the memory device MC3. However,such a sequence has little regularity, and is not arrange wellsequentially, such as writing data to the lower pages of the memorydevices MC0 to MC3, then writing data to the middle pages of the memorydevices MC0 to MC3, then writing data to the upper pages of the memorydevices MC0 to MC3, and then writing data to the top pages of the memorydevices MC0 to MC3, for example.

According to the 13th embodiment, the transmission of the command setsfor writing data sets as illustrated in the 13th embodiment is highlyregular. In other words, for example, a sequence such as all data-writesdesignating the lower page, then all data-writes designating the middlepage, then all data-writes designating the upper page, and then alldata-writes designating the top page is possible. Even with such commandtransmission, data is written as illustrated in the 13th embodiment. Forthis reason, the instructions for data writing by the memory controller2 are simple, and the processing load on the memory controller 2 islight.

<13.5. Modification>

The conversion of designated pages by the address converter 18 or 19like in the 13th embodiment is also applicable to embodiments other thanthe third and 11th embodiments.

14th Embodiment

The 14th embodiment relates to details of read, and is applicable to thereading of data stored in any format. Hereinafter, the features thatdiffer from the first embodiment will be described mainly.

<14.1. Configuration>

FIG. 66 illustrates functional blocks of a memory controller 2 accordingto the 14th embodiment. Each functional block is realizable byoperations by the CPU 22 following firmware in the RAM 23, a portion ofthe memory space in the RAM 23, and/or dedicated hardware (or, acircuit).

The memory controller 2 includes a command generator 231, a commandqueue 232, and a command delivery unit 233. Of the plurality offunctions provided by the read controller 212, the command generator 231is responsible for generating the command sets described in the first to13th embodiments. The command generator 231 generates command setsaccording to a first-in first-out rule, for example. In other words, thecommand generator 231 generates command sets in the same order as theorder in which the command generator 231 determines the generation ofthe command sets, on the basis of information such as instructions fromthe host device 200.

The command queue 232 holds the command sets generated by the commandgenerator 231 in the generated order. In other words, a command setgenerated earlier is assigned a higher order of priority.

The command delivery unit 233 transmits the command sets held in thecommand queue 232 to the memory interface 25 in an order rearrangedaccording to a certain rule. The memory interface 25 transmits thecommand sets to the memory device MC in the order in which the commandsets were received from the command delivery unit 233.

<14.2. Operations>

The following description and related diagrams relate to an example ofthe storage of two bits of data per memory cell transistor, the same asthat described in the 11th embodiment. However, the 14th embodiment isalso applicable to an example of the storage of three or more bits ofdata per memory cell transistor. The details can be inferred by personsskilled in the art on the basis of the principles described below.

The memory device MC uses the same 12 mapping as the 11th embodiment,such that each cell unit CU stores data of two pages in size, and thetwo pages include just one fast page. Also, like the 11th embodiment,the following description relates to an example in which the planes PB0and PB1 in each memory device MC cannot operate independently.

FIG. 67 illustrates a flow of data reads in the memory system 100according to the 14th embodiment, and more specifically, illustrates aflow of operations by the read controller 212. As illustrated in FIG.67, the command generator 231 determines whether N read command sets arebeing held in the command queue 232 (step ST31). N is any number. Asdescribed later, the read controller 212 rearranges, for each N commandset, an order in which to deliver the N command sets. For this reason,the order in which the command sets are generated and the order in whichthe command sets are delivered may be different, and there is apossibility of a delay in the delivery of a command set generatedearlier. It is possible to determine N such that this delay does notviolate the constraints that the memory system 100 should satisfy. Thefollowing description is based on an example where N is 4.

In the case where N read command sets are not being held in the commandqueue 232 (No branch of step ST31), the process proceeds to step ST32.In step ST32, the command generator 231 generates a read command set onthe basis of the occurrence of processes to be executed. Step ST32continues to step ST31.

In the case where N read command sets are being held in the commandqueue 232 (Yes branch of step ST31), the process proceeds to step ST33.In step ST33, the command delivery unit 233 determines whether the Ncommand sets include a command set targeting a memory device MC and acommand set targeting another memory device MC. In the case wherecommand sets targeting different memory devices MC are not included (Nobranch of step ST33), the process proceeds to step ST35. In step ST35,the command delivery unit 233 transmits the N command sets to the targetmemory devices MC through the memory interface 25 in the currentarrangement, that is, in the current order of priority.

In the case where command sets targeting different memory devices MC areincluded, the process proceeds to step ST36. In step ST36, the commanddelivery unit 233 rearranges the order of the N command sets in thecommand queue 232 such that the command set targeting a memory device MCis followed by the command set targeting another memory device MC. Forexample, in the case where four command sets arranged in the generatedorder target the memory devices MC0, MC0, MC1, and MC1, respectively,the command delivery unit 233 rearranges the command sets into the orderof a command set targeting the memory device MC0, a command settargeting the memory device MC1, a command set targeting the memorydevice MC0, and a command set targeting the memory device MC1.

Hereinafter, rearranging the order of command sets CS and changing thepriorities assigned to command sets CS refer to the same process.

The command delivery unit 233 determines whether the N command setsinclude a command set for a non-fast page and a command set for a fastpage (step ST38). In the case where the N command sets do not includeboth a read command set for a non-fast page and a read command set for afast page (No branch of step ST38), the process proceeds to step ST35.

In the case where the N command sets include both a read command set fora non-fast page (non-fast page command set) CS and a read command settargeting a fast page (fast page command set) CS (Yes branch of stepST38), the process proceeds to step ST39. In step ST39, the commanddelivery unit 233 rearranges the N command sets such that a fast pagecommand set CS is followed by a non-fast page command set CS, while alsomaintaining the arrangement in which consecutive command sets CS targetdifferent memory devices MC. To this end, in the arrangement of the Ncommand sets, the command delivery unit 233 can substitute each fastpage command set with a different command set for the memory device MCtargeted by the fast page command set among the N command sets. Throughthe rearrangement in step ST39, at least one fast page command set CS ismoved to the front of the order of the N command sets CS.

Step ST39 continues to step ST35. When step ST35 ends, the flow in FIG.67 ends. In the case where α read command set still exists, the flow inFIG. 67 starts from step ST31.

Hereinafter, FIGS. 68 to 70 will be referenced to describe threeexamples of rearranging read command sets.

FIGS. 68 to 70 illustrate states of the command queue 232 duringoperations over time in the memory system 100 according to the 14thembodiment. Specifically, FIGS. 68 to 70 respectively illustrate a firstexample, a second example, and a third example of the state of thecommand queue during the flow of FIG. 67, and relate to an example ofN=4.

The portion (a) of FIG. 68 illustrates the state at the start of stepST33. As an example, the four command sets include command sets CS00,CS01, CS10, and CS11. The command set CS00 designates a read from anon-fast page of the memory device MC0. The command set CS01 designatesa read from a non-fast page of the memory device MC0. The command setCS10 designates a read from a non-fast page of the memory device MC1.The command set CS11 (shaded in the diagram) designates a read from afast page of the memory device MC1. The command sets CS00, CS01, CS10,and CS11 are generated in that order. For this reason, the command setsCS00, CS01, CS10, and CS11 are arranged by decreasing priority in thatorder.

The portion (b) of FIG. 68 illustrates the state at the end of stepST36. The command sets CS00, CS01, CS10, and CS11 have been rearrangedsuch that a command targeting the memory device MC0 is adjacent to acommand targeting the memory device MC1. As a result, for example, thecommand sets CS00, CS10, CS01, and CS11 are arranged by decreasingpriority in that order.

The portion (c) of FIG. 68 illustrates the state at the end of stepST39. The command set CS11 targeting a fast page is moved to the frontof the order of priority. Even after the move, the remaining commandsets CS00, CS01, and CS10 are still rearranged such that a commandtargeting the memory device MC0 is adjacent to a command targeting thememory device MC1. As a result, the command sets CS11, CS00, CS10, andCS01 are arranged by decreasing priority in that order.

The portion (a) of FIG. 69 illustrates the state at the start of stepST33. As an example, the four command sets include command sets CS00,CS01, CS11, and CS02. The command set CS02 designates a read from anon-fast page of the memory device MC0. The command sets CS00, CS01,CS11, and CS02 are generated in that order.

The portion (b) of FIG. 69 illustrates the state at the end of stepST39. As a result of rearrangement, the only fast page command set CS11is positioned at the beginning of the order of priority, and is followedby a command set that targets the memory device MC0, which is differentfrom the memory device MC1, which is the target of the fast page commandset CS11, such as the command set CS00 for example. Because there is noother command set CS targeting the memory device MC1, the command setCS00 is followed by the command sets targeting the memory device MC0,such as the command sets CS01 and CS02 in that order, for example.

The portion (a) of FIG. 70 illustrates the state at the start of stepST33. As an example, the four command sets include command sets CS00,CS03, CS10, and CS11. The command set CS03 designates a read from a fastpage of the memory device MC0. The command sets CS00, CS03, CS10, andCS11 are generated in the above order.

The portion (b) of FIG. 70 illustrates the state at the end of stepST39. As a result of rearrangement, the fast page command set CS03 ispositioned at the beginning of the order of priority, and is followed bythe command set CS11, which targets the memory device MC1, which isdifferent from the memory device MC0, which is the target of the commandset CS03. The command set CS00 targeting the memory device MC0, which isdifferent from the memory device MC1, which is the target of the commandCS11, follows next, and is followed by the remaining command set CS10.

<14.3. Advantages>

Depending on the order in which the read command sets are generated, ifthe read command sets are transmitted in the generated order, theexecution of the reads may be time-consuming in some cases. For example,the command sets CS00, CS01, CS10, and CS11 generated in the orderillustrated in the portion (a) of FIG. 68 can be rearranged such thatcommand sets CS targeting different memory devices MC are adjacent toeach other, as illustrated in the portion (b) of FIG. 68. Thisarrangement makes it possible to proceed with reads by a plurality ofcommand sets in parallel. However, the command set CS11 targeting a fastpage comes after the command set CS01 targeting a non-fast page. Forthis reason, even though preparations are complete for the output ofpage data PG by the command set CS11, it is necessary to wait for theread and the output of the obtained page data PG by the command setCS01.

According to the 14th embodiment, a plurality of command sets CS aretransmitted from the memory controller 2 in an order such that a fastpage command set CS is positioned in front and is also followed by acommand set CS targeting another memory device MC, and also such that afast page command set CS is followed by a non-fast page command set CS,regardless of the generated order.

For this reason, the start of a read from a certain fast page of acertain memory device MC is followed by the start of a read from acertain non-fast page of another memory device MC, while in addition,the non-fast page read is started after the start of the fast page readin another memory device MC, regardless of the order in which the readcommand sets are generated. This makes it possible to output the data ofthe fast page while the non-fast page read is in progress. Consequently,it is possible to read and output data with the same efficiency as thefirst embodiment according to the same principle as the firstembodiment.

<14.4. Modification>

The description so far relates to an example in which the commanddelivery unit 233 is included in the read controller 212. The 14thembodiment is not limited to this example. For example, the commanddelivery unit 233 may also be a part of the functions of the memoryinterface 25.

15th Embodiment

The 15th embodiment relates to an extension of the first to 11thembodiments, and is applicable to the first to 14th embodiments.

<15.1. Structure (Configuration)>

FIG. 71 illustrates components and connections in a memory systemaccording to a 15th embodiment, and related components. As illustratedin FIG. 71, the memory system 100 according to the 15th embodiment isdifferent from the configuration according to the first embodiment(FIG. 1) with regard to the memory controller 2 and the memory devicesMC. In general, the memory system 100 according to the 15th embodimentincludes two or more sets of the memory interface 25 according to thefirst embodiment and one or more memory devices MC connected to thatmemory interface 25. Hereinafter, the memory system 100 and the memorycontroller 2 according to the 15th embodiment may be referred to as thememory system 100A and the memory controller 2A, respectively, fordistinction.

The memory controller 2A includes a plurality of memory interfaces 25.FIG. 71 and the following description are based on an example in whichthe memory system 100 includes two sets, and consequently the memorycontroller 2A includes two memory interfaces 25A and 25B. The memoryinterfaces 25A and 25B have the same configuration as the memoryinterface 25.

The memory interface 25A is connected to one or more memory devices MCA(MCA0, MCA1, and so on). The memory interface 25B is connected to one ormore memory devices MCB (MCB0, MCB1, and so on). Each memory interface25 and the memory devices MCS connected to each memory interface 25 areconnected similarly to the connection between the memory interface 25and the one or more memory devices MC in the first embodiment (FIG. 1).

FIG. 72 illustrates functional blocks of the memory controller 2Aaccording to the 15th embodiment. Each functional block is realizable byoperations by the CPU 22 following firmware in the RAM 23, a portion ofthe memory space in the RAM 23, and/or dedicated hardware (or, acircuit). As illustrated in FIG. 72, the memory controller 2A includesthe memory interfaces 25A and 25B instead of the memory interface 25.

<15.2. Operations>

The memory controller 2A writes data to the memory devices MC asdescribed below. Hereinafter, the case of an extension of the secondembodiment is described as an example. In other words, the 4434 mappingis used, and each memory device MC includes the planes PB0 and PB1capable of operating independently. Also, in each of the memory deviceMCA and the memory device MCB, the memory area unit MA2 is configured asin the second embodiment. The memory area unit MA2 of the memory deviceMCA is referred to as the memory area unit MA2A, and the memory areaunit MA2 of the memory device MCB is referred to as the memory area unitMA2B.

The memory area unit MA2A is the set of the lower, middle, upper, andtop pages of a cell unit CUs00 in a plane PB0 of a memory device MCA0,the lower, middle, upper, and top pages of a cell unit CUs01 in a planeP21 of the memory device MCA0, the lower, middle, upper, and top pagesof a cell unit CUs10 in a plane PB0 of a memory device MCA1, and thelower, middle, upper, and top pages of a cell unit CUs11 in a plane PB1of the memory device MCA1.

The memory area unit MA2B is the set of the lower, middle, upper, andtop pages of a cell unit CUs00 in a plane PB0 of a memory device MCB0,the lower, middle, upper, and top pages of a cell unit CUs01 in a planePB1 of the memory device MCB0, the lower, middle, upper, and top pagesof a cell unit CUs10 in a plane PB0 of a memory device MCB1, and thelower, middle, upper, and top pages of a cell unit CUs11 in a plane PB1of the memory device MCB1.

Based on such features of the memory area units MA2A and MA2B, 32 piecesof page data PG with consecutive logical addresses are stored in asingle memory area unit MA2A or MA2B. Additionally, 16 pieces of pagedata PG with certain logical addresses are held in the memory area unitMA2A, while the 16 pieces of page data PG with the remaining logicaladdresses are held in the memory area unit MA2B.

Next, FIGS. 73 to 75 will be referenced to describe specific first tothird examples of writing. FIGS. 73 to 75 respectively illustrate firstto third examples of the memory area units MA2 and positions where pagedata are written in the memory devices MC according to the 15thembodiment. In general, 32 pieces of page data PG with consecutivelogical addresses are written in a distributed manner to the memory areaunits MA2A and MA2B, similarly to the second embodiment.

15.2.1. First Example

As illustrated in FIG. 73, the 32 pieces of page data PG withconsecutive logical addresses are alternately written to the memory areaunits MA2A and MA2B in order of ascending logical address. In otherwords, page data PG(2γ) is written to the memory area unit MA2Aaccording to a rule by which the descriptions regarding the page dataPG0 to PG15 in the second embodiment are applied to the page data PG(2γ)for the cases of γ from 0 to 15, respectively. Additionally, page dataPG(2γ+1) is written to the memory area unit MA2B according to a rule bywhich the descriptions regarding the page data PG0 to PG15 in the secondembodiment are applied to the page data PG(2γ+1) for the cases of γ from0 to 15, respectively. Details are as follows.

For each of the cases where δ is 0, 1, 8, 9, 16, 17, 24, and 25, thepage data PGδ, PG(δ+2), PG(δ+4), and PG(δ+6) form a data set.

As illustrated in FIG. 73, for each of the cases where δ is 0, 8, 16,and 24, each one of the page data PG6, PG(δ+2), PG(δ+4), and PG(δ+6) ofeach data set is written to a different one of all combinations of theplanes PB0 and PB1 of the memory devices MCA0 and MCA1, and in addition,one of the page data PG5, PG(δ+2), PG(δ+4), and PG(δ+6) is written to afast page (upper page) while the remaining three are written to non-fastpages. Also, each piece of page data included in a data set and writtento a non-fast page is written to any of the lower, middle, and toppages. Furthermore, the pages to which the page data PG0, PG2, PG4, PG6,PG8, PG10, PG12, PG14, PG16, PG18, PG20, PG22, PG24, PG26, PG28, andPG30 are written are determined such that four data sets are written tothe memory area unit MA2A. Insofar as the pages are written in this way,the positions where the page data PG0, PG2, PG4, PG6, PG8, PG10, PG12,PG14, PG16, PG18, PG20, PG22, PG24, PG26, PG28, and PG30 are written arenot limited to the example in FIG. 73. As an example, the page data PGwritten to the non-fast pages can be written to different one of lower,middle, and top pages.

Also, for each of the cases where δ is 1, 9, 17, and 25, each one of thepage data PG5, PG(δ+2), PG(δ+4), and PG(δ+6) of each data set arewritten to a different one of all combinations of the planes PB0 and PB1of the memory devices MCB0 and MCB1, and in addition, one of the pagedata PGδ, PG(δ+2), PG(δ+4), and PG(δ+6) is written to a fast page (upperpage) while the remaining three are written to non-fast pages. Also,each piece of page data included in a data set and written to a non-fastpage is written to any of the lower, middle, and top pages. Furthermore,the pages to which the page data PG1, PG3, PG5, PG7, PG9, PG11, PG13,PG15, PG17, PG19, PG21, PG23, PG25, PG27, PG29, and PG31 are written aredetermined such that four data sets are written to the memory area unitMA2B. Insofar as the pages are written in this way, the positions wherethe page data PG1, PG3, PG5, PG7, PG9, PG11, PG13, PG15, PG17, PG19,PG21, PG23, PG25, PG27, PG29, and PG31 are written are not limited tothe example in FIG. 73. As an example, the page data PG written to thenon-fast pages can be written to different one of lower, middle, and toppages.

As illustrated in FIG. 73, the page data PG0 is written to the upperpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MCA0. The page data PG1 is written to the upper page of theselected cell unit CUs00 in the plane PB0 of the memory device MCB0. Thepage data PG2 is written to the middle page of the selected cell unitCUs01 in the plane PB1 of the memory device MCA0. The page data PG3 iswritten to the middle page of the selected cell unit CUs01 in the planePB1 of the memory device MCB0. The page data PG4 is written to the lowerpage of the selected cell unit CUs10 in the plane PB0 of the memorydevice MCA1. The page data PG5 is written to the lower page of theselected cell unit CUs10 in the plane PB0 of the memory device MCB1. Thepage data PG6 is written to the top page of the selected cell unit CUs11in the plane PB1 of the memory device MCA1. The page data PG7 is writtento the top page of the selected cell unit CUs11 in the plane PB1 of thememory device MCB1.

The page data PG8 is written to the upper page of the selected cell unitCUs00 in the plane PB1 of the memory device MCA0. The page data PG9 iswritten to the upper page of the selected cell unit CUs00 in the planePB1 of the memory device MCB0. The page data PG10 is written to themiddle page of the selected cell unit CUs00 in the plane PB0 of thememory device MCA0. The page data PG11 is written to the middle page ofthe selected cell unit CUs00 in the plane PB0 of the memory device MCB0.The page data PG12 is written to the lower page of the selected cellunit CUs11 in the plane PB1 of the memory device MCA1. The page dataPG13 is written to the lower page of the selected cell unit CUs11 in theplane PB1 of the memory device MCB1. The page data PG14 is written tothe top page of the selected cell unit CUs10 in the plane PB0 of thememory device MCA1. The page data PG15 is written to the top page of theselected cell unit CUs10 in the plane PB0 of the memory device MCB1.

The page data PG16 is written to the upper page of the selected cellunit CUs10 in the plane PB0 of the memory device MCA1. The page dataPG17 is written to the upper page of the selected cell unit CUs10 in theplane PB0 of the memory device MCB1. The page data PG18 is written tothe middle page of the selected cell unit CUs11 in the plane PB1 of thememory device MCA1. The page data PG19 is written to the middle page ofthe selected cell unit CUs11 in the plane PB1 of the memory device MCB1.The page data PG20 is written to the top page of the selected cell unitCUs00 in the plane PB0 of the memory device MCA0. The page data PG21 iswritten to the top page of the selected cell unit CUs00 in the plane PB0of the memory device MCB0. The page data PG22 is written to the lowerpage of the selected cell unit CUs01 in the plane PB1 of the memorydevice MCA0. The page data PG23 is written to the lower page of theselected cell unit CUs01 in the plane PB1 of the memory device MCB0.

The page data PG24 is written to the upper page of the selected cellunit CUs1 l in the plane PB1 of the memory device MCA1. The page dataPG25 is written to the upper page of the selected cell unit CUs11 in theplane PB1 of the memory device MCB1. The page data PG26 is written tothe middle page of the selected cell unit CUs10 in the plane PB0 of thememory device MCA1. The page data PG27 is written to the middle page ofthe selected cell unit CUs10 in the plane PB0 of the memory device MCB1.The page data PG28 is written to the top page of the selected cell unitCUs01 in the plane PB1 of the memory device MCA0. The page data PG29 iswritten to the top page of the selected cell unit CUs01 in the plane PB1of the memory device MCB0. The page data PG30 is written to the lowerpage of the selected cell unit CUs00 in the plane PB0 of the memorydevice MCA0. The page data PG31 is written to the lower page of theselected cell unit CUs00 in the plane PB0 of the memory device MCB0.

Data reads are the same as those in the second embodiment, except foroccurring in the memory devices MCA and MCB in parallel. In other words,in each of the memory area units MA2A and MA2B, reads can proceedaccording to a rule by which the descriptions regarding the 16 pieces ofpage data PG with consecutive logical address in the second embodimentare applied to 16 pieces of page data PG with alternating logicaladdresses.

15.2.2. Second Example

As illustrated in FIG. 74, the 32 pieces of page data PG withconsecutive logical addresses are alternately written to the memory areaunits MA2A and MA2B in order of ascending logical address for every fourpieces of page data PG with certain logical addresses. Specifically, thepage data PGγ, PG(γ+1), PG(γ+4), and PG(γ+5) are written to the memoryarea unit MA2A according to a rule where the descriptions regarding thepage data PG0 to PG15 in the second embodiment are applied to the pagedata PGγ, PG(γ+1), PG (γ+4), and PG (γ+5) in ascending order for each ofthe cases where γ is 0, 8, 16, and 24. Furthermore, the page data PGγ,PG(γ+1), PG(γ+4), and PG(γ+5) are written to the memory area unit MA2Baccording to a rule where the descriptions regarding the page data PG0to PG15 in the second embodiment are applied to the page data PGγ,PG(γ+1), PG(γ+4), and PG(γ+5) in ascending order for each of the caseswhere γ is 2, 10, 18, and 26. Details are as follows.

For each of the cases where δ is 0, 2, 8, 10, 16, 18, 24, and 26, thepage data PG, PG(δ+1), PG(δ+4), and PG(δ+5) form a data set.

As illustrated in FIG. 74, for each of the cases where δ is 0, 8, 16,and 24, each one of the page data PG5, PG(δ+1), PG(δ+4), and PG(δ+5) ofeach data set is written to a different one of all combinations of theplanes PB0 and PB1 of the memory devices MCA0 and MCA1, and in addition,one of the page data PG5, PG(δ+1), PG(δ+4), and PG(δ+5) is written to afast page (upper page) while the remaining three are written to non-fastpages. Also, each piece of page data included in a data set and writtento a non-fast page is written to any of the lower, middle, and toppages.

Furthermore, the pages to which the page data PG0, PG1, PG4, PG5, PG8,PG9, PG12, PG13, PG16, PG17, PG20, PG21, PG24, PG25, PG28, and PG29 arewritten are determined such that four data sets are written to thememory area unit MA2A. Insofar as the pages are written in this way, thepositions where the page data PG0, PG1, PG4, PG5, PG8, PG9, PG12, PG13,PG16, PG17, PG20, PG21, PG24, PG25, PG28, and PG29 are written are notlimited to the example in FIG. 74. As an example, the page data PGwritten to the non-fast pages can be written to different one of lower,middle, and top pages.

Also, for each of the cases where δ is 2, 10, 18, and 26, each of thepage data PG6, PG(δ+1), PG(δ+4), and PG(δ+5) of each data set is writtento a different one of all combinations of the planes PB0 and PB1 of thememory devices MCB0 and MCB1, and in addition, one of the page data PGδ,PG(δ+1), PG(δ+4), and PG(δ+5) is written to a fast page (upper page)while the remaining three are written to non-fast pages. Also, eachpiece of page data included in a data set and written to a non-fast pageis written to any of the lower, middle, and top pages. Furthermore, thepages to which the page data PG2, PG3, PG6, PG7, PG10, PG11, PG14, PG15,PG18, PG19, PG22, PG23, PG26, PG27, PG30, and PG31 are written aredetermined such that four data sets are written to the memory area unitMA2B. Insofar as the pages are written in this way, the positions wherethe page data PG2, PG3, PG6, PG7, PG10, PG11, PG14, PG15, PG18, PG19,PG22, PG23, PG26, PG27, PG30, and PG31 are written are not limited tothe example in FIG. 74. As an example, the page data PG written to thenon-fast pages can be written to different one of lower, middle, and toppages.

Data reads are the same as those in the second embodiment, except foroccurring in the memory devices MCA and MCB in parallel. In other words,in each of the memory area units MA2A and MA2B, reads can proceedaccording to a rule where the descriptions regarding the 16 pieces ofpage data PG with consecutive logical address in the second embodimentare applied to 16 pieces of page data PG with two consecutive logicaladdresses every four logical addresses.

15.2.3. Third Example

As illustrated in FIG. 75, the 32 pieces of page data PG withconsecutive logical addresses are alternately written to the memory areaunits MA2A and MA2B in order of ascending logical address for every fourpieces of page data PG with consecutive logical addresses. Specifically,the page data PGγ, PG(γ+1), PG(γ+2), and PG(γ+3) are written to thememory area unit MA2A according to a rule where the descriptionsregarding the page data PG0 to PG15 in the second embodiment are appliedto the page data PGγ, PG(γ+1), PG (γ+2), and PG (γ+3) in ascending orderfor each of the cases where γ is 0, 8, 16, and 24. Furthermore, the pagedata PGγ, PG(γ+1), PG (γ+2), and PG(γ+3) are written to the memory areaunit MA2B according to a rule where the descriptions regarding the pagedata PG0 to PG15 in the second embodiment are applied to the page dataPGγ, PG(γ+1), PG(γ+2), and PG(γ+3) in ascending order for each of thecases where γ is 4, 12, 20, and 28. Details are as follows.

For each of the cases where δ is 0, 4, 8, 12, 16, 20, 24, and 28, thepage data PG5, PG(δ+1), PG(δ+2), and PG(δ+3) form a data set.

As illustrated in FIG. 75, for each of the cases where δ is 0, 8, 16,and 24, each of the page data PGδ, PG(δ+1), PG(δ+2), and PG(δ+3) of eachdata set is written to a different one of all combinations of the planesPB0 and PB1 of the memory devices MCA0 and MCA1, and in addition, one ofthe page data PG5, PG(δ+1), PG(δ+2), and PG(δ+3) is written to a fastpage (upper page) while the remaining three are written to non-fastpages. Also, each piece of page data included in a data set and writtento a non-fast page is written to any of the lower, middle, and toppages. Furthermore, the pages to which the page data PG0, PG1, PG2, PG3,PG8, PG9, PG10, PG11, PG16, PG17, PG18, PG19, PG24, PG25, PG26, and PG27are written are determined such that four data sets are written to thememory area unit MA2A. Insofar as the pages are written in this way, thepositions where the page data PG0, PG1, PG2, PG3, PG8, PG9, PG10, PG11,PG16, PG17, PG18, PG19, PG24, PG25, PG26, and PG27 are written are notlimited to the example in FIG. 75.

As an example, the page data PG written to the non-fast pages can bewritten to different one of lower, middle, and top pages.

Also, for each of the cases where δ is 4, 12, 20, and 28, each of thepage data PG5, PG(δ+1), PG(δ+2), and PG(δ+3) of each data set is writtento a different one of every combination of the planes PB0 and PB1 of thememory devices MCB0 and MCB1, and in addition, one of the page data PGδ,PG(δ+1), PG(δ+2), and PG(δ+3) is written to a fast page (upper page)while the remaining three are written to non-fast pages. Also, eachpiece of page data included in a data set and written to a non-fast pageis written to any of the lower, middle, and top pages. Furthermore, thepages to which the page data PG4, PG5, PG6, PG7, PG12, PG13, PG14, PG15,PG20, PG21, PG22, PG23, PG28, PG29, PG30, and PG31 are written aredetermined such that four data sets are written to the memory area unitMA2B. Insofar as the pages are written in this way, the positions wherethe page data PG4, PG5, PG6, PG7, PG12, PG13, PG14, PG15, PG20, PG21,PG22, PG23, PG28, PG29, PG30, and PG31 are written are not limited tothe example in FIG. 75. As an example, the page data PG written to thenon-fast pages can be written to different one of lower, middle, and toppages.

Data reads are the same as those in the second embodiment, except foroccurring in the memory devices MCA and MCB in parallel. In other words,in each of the memory area units MA2A and MA2B, reads can proceedaccording to a rule where the descriptions regarding the 16 pieces ofpage data PG with consecutive logical address in the second embodimentare applied to 16 pieces of page data PG with consecutive logicaladdresses every four logical addresses.

<15.3. Modification>

As described above, the 15th embodiment is applicable to any of thefirst embodiment and the third to 11th embodiments. In this case, theprinciples of the 15th embodiment described as being applied to thesecond embodiment above are applied to the applied embodiment. In otherwords, writes in the applied embodiment proceeds in parallel in thememory devices MCA and MCB as described above. The details can beinferred by persons skilled in the art from the description of the 15thembodiment.

<15.4. Advantages>

According to the 15th embodiment, the first to 11th embodiments can beapplied to each of a plurality of memory devices MC connected todifferent memory interfaces 25. Consequently, the same advantages as theapplied embodiment are obtained, even in the case where the memorysystem 100 includes a plurality of memory interfaces 25.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A memory system comprising: n (where n is anatural number equal to or greater than 2) memory cells, each capable ofstoring j (where j is a natural number equal to or greater than 2) bitsof data; and a controller configured to write a first portion of each offirst data to n-th data from among n×j data with consecutive logicaladdresses to the n memory cells one by one, wherein the first data has alowest logical address among the n×j pieces of data, the first data tothe n-th data have ascending consecutive logical addresses, and thecontroller is configured to write the first portion of one of the firstto n-th data as a first bit of the j bits, and write the first portionof another one of the first to n-th data except said one of the first ton-th data as a second bit of the j bits.
 2. The memory system accordingto claim 1, wherein the controller is configured to apply read voltagesto the n memory cells to read data in a bit among the j bits from the nmemory cells, and a number of read voltages for reading data in thefirst bit among the j bits from the n memory cells is smaller than anumber of read voltages for reading data in bits other than the firstbit.
 3. The memory system according to claim 1, wherein the n memorycells are respectively coupled to different bit lines through respectiveselect transistors, and the select transistors are respectively coupledat gates to different row decoders.
 4. The memory system according toclaim 1, wherein n is a natural number equal to or greater than 3, andthe controller is configured to write the first portion of each of thefirst to n-th data except said one of the first to n-th data as a bitdifferent from the first bit from among the j bits.
 5. The memory systemaccording to claim 1, further comprising n memory devices, wherein eachof the n memory devices includes one of the n memory cells.
 6. Thememory system according to claim 1, further comprising m (m being afactor of n) memory devices, wherein each of the m memory devicesincludes a set of n/m memory cells from among the n memory cells.
 7. Thememory system according to claim 1, further comprising: n word linesrespectively coupled to the n memory cells; and n potential generatorsrespectively coupled to the n word lines, wherein the n potentialgenerators are configured to output potentials of independent magnitudesat independent timings from each other.
 8. The memory system accordingto claim 1, wherein the controller is configured to transmit aninstruction to read the first portion of the first data, and transmit aninstruction to read the first portion of the second data subsequentlyafter the instruction to read the first portion of the first data. 9.The memory system according to claim 1, wherein n is 4, j is 4, thefirst bit is a bit read by applying three different voltages to a wordline coupled to one of the four memory cells, and the second bit is abit read by applying four or more different voltages to a word linecoupled to one of the four memory cells.
 10. The memory system accordingto claim 1, wherein n is 4, j is 4, the first bit is a bit read byapplying one voltage to a word line coupled to one of the four memorycells, and the second bit is a bit read by applying two or moredifferent voltages to a word line coupled to one of the four memorycells.
 11. The memory system according to claim 1, wherein n is 3, j is3, the first bit is a bit read by applying one voltage to a word linecoupled to one of the three memory cells, and the second bit is a bitread by applying two or more different voltages to a word line coupledto one of the three memory cells.
 12. The memory system according toclaim 1, wherein n is 3, j is 3, the first bit is a bit read by applyingtwo voltages to a word line coupled to one of the three memory cells,and the second bit is a bit read by applying three or more differentvoltages to a word line coupled to one of the three memory cells. 13.The memory system according to claim 1, wherein n is 2, j is 2, thefirst bit is a bit read by applying one voltage to a word line coupledto one of the two memory cells, and the second bit is a bit read byapplying two or more different voltages to a word line coupled to one ofthe two memory cells.
 14. A memory device comprising: a memory cellcapable of storing data as a first bit to a j-th bit (where j is anatural number equal to or greater than 2); and a first circuitconfigured to output a signal designating a second bit of the memorycell when the first circuit receives a signal designating the first bitwhile the first circuit is receiving a first signal having a firstvalue.
 15. The memory device according to claim 14, wherein the firstcircuit is further configured to output a signal designating the firstbit of the memory cell when the first circuit receives a signaldesignating the second bit while the first circuit is receiving thefirst signal having the first value.
 16. The memory device according toclaim 14, wherein the first circuit is further configured to output asignal designating a fourth bit of the memory cell when the firstcircuit receives a signal designating a third bit while the firstcircuit is receiving the first signal having a second value.
 17. Thememory system according to claim 1, further comprising p memory devices(where p is an integer factor of n), wherein the n memory cells aredistributed over the p memory devices, k data (where k is a naturalnumber) from among the first data to the n-th data are written to afirst memory device among the p memory devices, and k data from amongthe first data to the n-th data are written to the p-th memory device,the k data having respective logical addresses that are respectively(p−1) greater than the k data written to the first memory device.
 18. Amemory system comprising: first, second, and third memory cells, eachcapable of storing j (where j is a natural number equal to or greaterthan 2) bits of data; and a controller configured to apply, to the firstto third memory cells, read voltages to read data in a bit among the jbits from the first to third memory cells, wherein a number of readvoltages for reading data in a first bit among the j bits is smallerthan a number of read voltages for reading data in bits other than thefirst bit, a data read from the second memory cell and a data read fromthe third memory cell are capable of proceeding in parallel with a dataread from the first memory cell, a data read from the second memory celland a data read from the third memory cell is incapable of proceeding inparallel, and the controller is configured to generate a first commandset, a second command set, and a third command set in this order, thefirst command set being for reading data in a bit other than the firstbit of the first memory cell, the second command set being for readingdata in a bit other than the first bit of the second memory cell, thethird command set being for reading data in the first bit of the thirdmemory cell, and transmit the third command set, the first command set,and the second command set in this order.
 19. The memory systemaccording to claim 18, further comprising: a first memory device thatincludes the first memory cell; and a second memory device that includesthe second and third memory cells and is capable of operatingindependently from the first memory device.